
Stuart Kovinsky
posted a reply to Probability
in the Problem Solving forum
“Many probability questions can be solved intuitively rather than with long calculations. Let''s try to do so with this problem!
We can get off to a great start by flipping around the question: what''s the probability that Sally sits beside Andy?
We know that it has to go BGBGBGBGB. We can ...”



Stuart Kovinsky
posted a reply to Researchers
in the Sentence Correction forum
“One more approach!
The word "ancient" is a present use word  in other words, something is ancient from today''s perspective.
Accordingly, if we''re talking about a present discovery, we don''t say "what appeared to be an ancient hunting ground"; instead, we say "what ...”



Stuart Kovinsky
posted a reply to MGMAT Advanced Quant Visual Ques.
in the Problem Solving forum
“Hi Bharat!
Let''s start by breaking down the info  there''s actually a lot more there than you may think!
Possible scores are the integers 0 to 50, inclusive  that''s 51 possible scores.
100 people take the test.
At most, 2 people can get the same score.
Let''s assume for a moment that ...”



Stuart Kovinsky
posted a reply to Skeletal Heat
in the Critical Reasoning forum
“Hi Sid,
you''ll find some decent free resources on the net, you just have to be really careful. I''d always look for reviews of the source before diving in and using its questions. For all you know, those free questions were written by some bored guy living in his mom''s basement!
Depending ...”



Stuart Kovinsky
posted a reply to Combinatorics: Solution Explanation
in the Problem Solving forum
“Hi Dbloos!
That answer is in fact correct.
Here''s another way of looking at it: 2 out of the 14 patients will be chosen to receive P or R. Since the selection is random, each patient has a 2/14 chance of being one of the two.
We can confirm this answer with common sense (a very powerful ...”



Stuart Kovinsky
posted a reply to Samuel's Fishing Dilemma
in the Critical Reasoning forum
“Hi Siddhu,
a quick Google search reveals that this is yet another Platinum GMAT question, so it''s not surprising that it''s poorly constructed.
The problem here is different  there are 3 valid weakeners among the choices. So, instead of no good answer (like the previous Platinum GMAT ...”



Stuart Kovinsky
posted a reply to ENews Ads
in the Critical Reasoning forum
“Hi Siddhu!
This is another Platinum GMAT question  I''ve only seen 2 and I''m already superunimpressed.
There is no great weakener among the choices. For (C) to be relevant, we have to assume that "partners" means "people visiting one website will be faced with the same ...”



Stuart Kovinsky
posted a reply to Skeletal Heat
in the Critical Reasoning forum
“Hi Siddhu,
please always post your sources. A quick search of the Oracle (i.e. Google) revealed that this a question from Platinum GMAT, of whom I''ve never before heard.
This is a horrible question. None of the answers explain the paradox and, while a couple are classic traps, there is no ...”



Stuart Kovinsky
posted a reply to Dice
in the Problem Solving forum
“Hi Nipun!
The problem with treating this like a permutations problem  which is when you''d simply do 6*5*4  is that we don''t care about order, so you''re counting certain combinations multiple times.
For example, the 3 dice could come up as a 5, a 4 and a 3. However, they could also come ...”



Stuart Kovinsky
posted a reply to Quicker + alternate methods
in the Problem Solving forum
“Hi!
No such general formula exists  that pattern comes from an old GMAT question that gave you that summation as a rule to help you answer that one specific question. Whoever put it on a flashcard managed to confuse a whole bunch of people, though (which is why you should be very wary of ...”



Stuart Kovinsky
posted a reply to tenth digit in decimal representation
in the Data Sufficiency forum
“Hi! I''m assuming that this last part in quotes is your actually comment/question.
It''s important to know the place names for the various digits in a numbers, so let''s do a quick review, using the example of:
12345.6789
We start numbering to the left and the right of the decimal place. ...”



Stuart Kovinsky
posted a reply to MGMAT CAT Esteria vs Burdistan
in the Critical Reasoning forum
“Hi Julls!
This argument is a classic example of the most common pattern we see in critical reasoning: causation.
In a causal argument, the evidence describes some phenomenon and the conclusion is the author''s explanation for that phenomenon. In every causal argument, the author makes 3 ...”






Stuart Kovinsky
posted a reply to Lanuguages
in the Sentence Correction forum
“Hi!
I''ve bolded the part of the sentence relevant to your question.
Since we have "a language" in the nonunderlined part, "within it" is correct.
Also, it''s idiomatically correct to say "a dialect within a language", if that''s your main question. You could ...”



Stuart Kovinsky
posted a reply to To find the total amount of water in 3 glasses
in the Problem Solving forum
“Hi!
Uva did a great job saying what you could do next, so I want to discuss what you could have done instead  everyone taking the GMAT should strive to follow the Lazy Testtaker Rule: Do the least amount of work possible to answer each question.
On questions that ask you to find a range, ...”



Stuart Kovinsky
posted a reply to Integer Properties
in the Data Sufficiency forum
“I''m going to almost agree with Vipulgoyal, but say that the answer should be "C", together.
Also, I''m assuming that the question was correctly transcribed and the "different" wasn''t omitted from "does m have more than 5 prime factors"?
Since the Q stem omits ...”



Stuart Kovinsky
posted a reply to To find the average speed
in the Data Sufficiency forum
“Hi Sri!
You''ve assumed that the car''s speed is constant  which is exactly what the question is designed to trick you into assuming!
Remember: on the GMAT we only know what we''re explicitly told. Since we don''t know whether the car is travelling at a constant speed, there''s no way we ...”



Stuart Kovinsky
posted a reply to Rate Problem
in the Problem Solving forum
“Hi!
You haven''t provided any answer choices, so I''m a bit confused  is this a problem solving or a data sufficiency question?
You said that the OA is "6", but since we only have variables, how can the answer be an actual number?
Your equation for time to catch up is dead on, ...”



Stuart Kovinsky
posted a reply to Combinatorics.Plese help.
in the Problem Solving forum
“All you''re really doing when you apply the "slot method" to these problem is using the combinations formula:
nCk = n!/k!(nk)!
When order does NOT matter, that''s the formula we use.
So, if we''re simply choosing 4 out of 7 and we don''t care about order, we get:
7C4 = 7!/4!3! ...”



Stuart Kovinsky
posted a reply to What is the remainder?
in the Data Sufficiency forum
“Hi Sri!
For remainder questions, we often only need to look at the last 1 or 2 digits of the number. In this case, since we''re dividing by 5, only the last digit actually matters.
So, we can recognize the pattern for powers of 2:
2^1 = 2
2^2 = 4
2^3 = 8
2^4 = ..6
2^5 = ..2
and so ...”



Stuart Kovinsky
posted a reply to Need help on Percentage Question
in the Problem Solving forum
“Hi Scraby!
First, please always post the answer choices, since they play a large role in many GMAT strategies. On this question, for example, backsolving (working backwards from the choices) is almost certainly the quickest way to get the answer.
Let''s approach it via both algebra and ...”



Stuart Kovinsky
posted a reply to Most interns who work for pay hold positions...
in the Sentence Correction forum
“Hi!
This sentence is all about parallelism.
When we have a list, we have to make sure that all the parts are stated correctly. When each part of the list has the same modifier, you can just put that modifier at the beginning of the list. However, when different parts require different ...”



Stuart Kovinsky
posted a reply to What is the value of x  y ?
in the Data Sufficiency forum
“Hi Sri!
We know that both x and y are positive and that x is greater than y. We need to find an exact value for (xy).
1) tells us that root(x)  root(y) = 1
If we square both sides, we get:
(rootx  rooty)^2 = 1
x  2root(xy)  y = 1
well, since have no clue what x and y are, ...”



Stuart Kovinsky
posted a reply to Combinatorics.Plese help.
in the Problem Solving forum
“When we''re counting we''re always dealing with whole numbers: for example, there are never going to be 3.5 possible groups. So, as soon as you get a fraction, you know there''s a problem.
The problem with the using the "slot method" is that you''ve treated 2 different selections as ...”



Stuart Kovinsky
posted a reply to Probabilit
in the Problem Solving forum
“Hi!
This may look like a probability question, but it''s really all about geometry. The question is really asking "what portion of ABCD is shaded?"
This question is super quick if you use your graphlined noteboard to draw the shape to scale  you''ll quickly see that the mini ...”



Stuart Kovinsky
posted a reply to Probability Again
in the Problem Solving forum
“Hi! This question is a great illustrator of the "one minus" approach to complicated probability problems.
When you see "at least" or "at most" in probability, you''re going to be solving for multiple scenarios. However, it''s often quicker to solve for what you do ...”






Stuart Kovinsky
posted a reply to Club members at least 35yrs old
in the Data Sufficiency forum
“Hi! We only care about at least 35 vs below 35, so "children" are irrelevant.
Q: how many members are 35 or older?
We think: value question asking us to solve for an actual number, so we need info about numbers!
1) nothing about actual numbers (i.e. just a fraction)  ...”



Stuart Kovinsky
posted a reply to Square Root of Variables
in the Problem Solving forum
“Hi!
First, the problem you posted doesn''t actually include a question, so I''m not sure for what you''re solving. In other words, you posted an equation, but no question.
However, I can still answer your question  the official answer you posted and your answer are actually identical.
We ...”



Stuart Kovinsky
posted a reply to Bank fees
in the Sentence Correction forum
“Hi Eric!
This sentence is all about proper verb tenses  one of the most commonly tested issues in sentence correction.
Remember to always use the nonunderlined portion of the sentence (which is, by definition, correct) to guide your selection for the underlined portion.
Here, as soon as ...”



Stuart Kovinsky
posted a reply to Auto company profits
in the Sentence Correction forum
“Hi Eric!
Recognizing common GMAT idioms can help you cut to the heart of a SC question and ignore all the "fluff" that the GMAT includes to distract you.
There are two important idioms to recognize in this argument.
First, we "attribute to". However, since every ...”



Stuart Kovinsky
posted a reply to Mall Occupancy
in the Critical Reasoning forum
“Hi Lula!
Anyone who wants to be a top scorer on the GMAT needs to learn to recognize common patterns. This argument exemplifies one such pattern in critical reasoning.
It''s common for authors to identify a problem and then propose a solution. It''s also common for authors to go one step ...”



Stuart Kovinsky
posted a reply to Number Line Data Sufficiency
in the Data Sufficiency forum
“Hi!
In geometry, whenever two points are put together like that, they always describe the line formed by connecting them. The same rule applies to number lines, which are really just a form of linear geometry.”



Stuart Kovinsky
posted a reply to Please can you explain the reasoning behind this?
in the Problem Solving forum
“Hi!
We''re told that x is positive and increasing and we''re asked to determine which of 3 expressions will increase along with x.
Here''s something to remember: the GMAT is not trying to be your friend, but it is trying to see how clever you are. So, we''re always using our cleverness to ...”



Stuart Kovinsky
posted a reply to Pls explain the calculation
in the Problem Solving forum
“Hi!
This question is testing your ability to find limits and estimate.
We''re told that K is the sum of the reciprocals of the integers 43 through 48, inclusive. In other words:
K = 1/43 + 1/44 + 1/45 + 1/46 + 1/47 + 1/48
well, that''s a whole mess of ugly math, so there''s got to be a ...”



Stuart Kovinsky
posted a reply to Data Sufficiency Qs
in the Problem Solving forum
“Hi!
What''s the source of this question? I''m asking because, technically, the 4 brothers could be quadruplets and all the same age. I really doubt that the question intends for that to be a possibility and the GMAT would never leave that ambiguity in place. Let''s assume that the question ...”



Stuart Kovinsky
posted a reply to Pls help with the solution
in the Problem Solving forum
“Hi!
First, I''m not sure if the image I uploaded will work  for some reason the IMG uploader isn''t giving me any love! So, I''ve attached it as a document as well.
In any case, let''s break the question down.
We''re told that ABC are 3 points in the coordinate plane that do not form a ...”



Stuart Kovinsky
posted a reply to 650level Combinatorics problem.Please help
in the Problem Solving forum
“Hey Dan!
I''m glad that the question makes sense now.
Kaplan''s Premier Guide has a chapter devoted to statistics, which includes perms & combs (and of course those questions show up on our CATs). Whether that''s "enough" to get you through to test day depends on how much work ...”






Stuart Kovinsky
posted a reply to Verb Tense, Mood, & Voice  MGMT SC
in the Sentence Correction forum
“Hi Ian!
Great job identifying that this sentence calls for the subjunctive mood. I like that term "bossy verb"  I''m going to steal that and pretend I made it up!
Here''s the bare syntax for using the subjunctive:
[subject 1] [bossy/question verb] that [subject 2] [infinitive ...”



Stuart Kovinsky
posted a reply to Median question
in the Data Sufficiency forum
“Hi!
Here''s a thread that discusses this problem in detail:
[url]http://www.beatthegmat.com/medianquestiont8140.html[/url]
If you still have questions about it, ask away!
Stuart”



Stuart Kovinsky
posted a reply to 650level Combinatorics problem.Please help
in the Problem Solving forum
“No  the question is written in such a way that those 2 people are fixed (even if they''re not named). For the purposes of our calculation, it doesn''t matter which 2 people don''t get along.
Now I feel like you''re arguing just for the sake of arguing!
:D”



Stuart Kovinsky
posted a reply to 650level Combinatorics problem.Please help
in the Problem Solving forum
“Here''s the key difference: there''s only one way to choose the 2 consultants who can''t be together. There are multiple ways to choose the 8 male members of the jury.
Technically, when calculating the number of disqualified teams of consultants, we''re calculating:
2C2 * 5C2 = 1*10 = 10
...”



Stuart Kovinsky
posted a reply to 1000CR Test 4 Q14
in the Critical Reasoning forum
“Hi Aditya!
The opponents argue that people should be free to decide whether to wear seatbelts based on the rule that "you can do what you want as long as you don''t harm OTHERS".
(e) doesn''t weaken because the nonseatbelt wearers are only harming themselves  something the ...”



Stuart Kovinsky
posted a reply to 650level Combinatorics problem.Please help
in the Problem Solving forum
“In this part of the solution, you''re ONLY looking at the unacceptable teams. In other words, you''re counting how many teams are disqualified due to inclusion of the 2 archenemies.
Since we only care about disqualifying teams including the 2 troublemakers, we automatically include both of them ...”






Stuart Kovinsky
posted a reply to 650level Combinatorics problem.Please help
in the Problem Solving forum
“Speaking specifically to your solution, the problem in each case is when you begin with:
There are 10 males total, so there are 10C8 ways to select those 8 males. You need to factor all those possibilities into your solution as well. (10C8 = 10*9/2*1 = 45)
In the second case, you have to ...”






Stuart Kovinsky
posted a reply to Functions f(x)
in the Problem Solving forum
“Hi!
The most effective (and sometimes only) way to approach Twopart Analysis questions in IR is backsolving: using the choices to generate the matching pair of answers.
There''s an infinite number of solutions for the problem, which is why you can''t "frontsolve" them. Instead of ...”



Stuart Kovinsky
posted a reply to interesting CR
in the Critical Reasoning forum
“Hi again!
One thing that it''s very important to remember: we accept the evidence as true. It''s not our job to discredit the evidence itself, but rather how the author uses that evidence. The vulnerable part of every argument is always the author''s assumptions: the missing but necessary ...”



Stuart Kovinsky
posted a reply to interesting CR
in the Critical Reasoning forum
“The GMAT is written according to patterns; understanding those patterns and how the test works gives you a huge advantage over your competitors.
Here, we''re asked to weaken the argument. So, we need to break it down and determine what the author is assuming, then look for an answer that attacks ...”



Stuart Kovinsky
posted a reply to weighted averages
in the Problem Solving forum
“A mixture of 20 grams of lean ground beef is mixed with 50 grams of fatty ground beef to create a ground beef mix with 8% fat. How many grams of fat does the lean ground beef have?
The ratio of fat content for L:F is 2:5. So, as GGNY (does he have a real name  does anyone know it?) aptly ...”



Stuart Kovinsky
posted a reply to Equilateral triangle inscribed in a circle
in the Problem Solving forum
“Hi!
There''s an excellent chance that on test day you''ll see a question that involves the circle sector formula  that''s exactly what we have here.
Here''s the formula:
length of arc/circumference = angle of arc/360 = area of sector/area of circle
In other words, every aspect of the ...”



Stuart Kovinsky
posted a reply to x divisible by 6?
in the Data Sufficiency forum
“Hi there!
Not much to dissect for the q stem: we can rephrase it as "is x a multiple of 6?" No info provided, so we know nothing!
(1) (x+3) is a multiple of 3, which means that x is also a multiple of 3.
if x=3, then x is NOT divisible by 6.
if x=6, then x IS divisible by 6.
...”



Stuart Kovinsky
posted a reply to line k in xyplane
in the Data Sufficiency forum
“Hi there!
We know that line K passes through the origin, so it must pass through exactly 2 of the 4 quadrants (ab isn''t 0, so we know that line K isn''t just one of the axes).
Q: is b positive? We need info about which quadrant point a,b is in.
(1) the slope is negative.
If the slope ...”



Stuart Kovinsky
posted a reply to Square inscribed within a circle
in the Data Sufficiency forum
“Hi!
1. yes, they do (the diagonals of nonsquare rectangles also bisect each other, but not at right angles).
2. yes! The 4 angles have to add to 360 and they''re equal, so each one is 90 degrees.
And, in case anyone is wondering, each statement is sufficient since each one proves that ...”



Stuart Kovinsky
posted a reply to Pigs or cows
in the Data Sufficiency forum
“Quick note: as written, (1) is both sufficient and impossible. Brent corrected the statement in his explanation.
(I say (1) is impossible because it would require the farm to have (2/3)(40) = 26 2/3 cows, which is both messy and illegal in some states.)”



Stuart Kovinsky
posted a reply to discounted airline tickets
in the Critical Reasoning forum
“Hi!
What''s the source of this question? The author definitely isn''t assuming (b), so if that''s the accredited answer, it''s just a bad question.
The author is, on the other hand, assuming (a)  so your first instinct is correct!
Breaking down the stimulus:
Old plan had cheap prices ...”



Stuart Kovinsky
posted a reply to weighted averages
in the Problem Solving forum
“Sure  based on the original question, both the lean and the fatty could be 8% (or many many other combinations) and generate a different # of grams of fat. You have 2 unknowns but only 1 equation, so there''s an infinite number of solutions.
Stuart”






Stuart Kovinsky
posted a reply to proportion of women
in the Critical Reasoning forum
“Hi!
When asked to find the answer that would most help you evaluate the argument, look for the gap  in other words, the author''s assumption. The correct answer will be directly relevant to determining whether the assumption is valid.
Here, we have a classic scope shift. The author is ...”



Stuart Kovinsky
posted a reply to Source : GMAT PREP :New Q for old stimuli.
in the Critical Reasoning forum
“Certain patterns recur regularly in CR  possibly the most common argument form is causation.
We can paraphrase this entire argument as "the increase in price is responsible for the decrease in sales".
The most common ways to strengthen a causal argument are:
1) eliminate ...”






Stuart Kovinsky
posted a reply to Combinations 600 level problem..Please help
in the Problem Solving forum
“Hi Dan!
You''re right, this question is as much about logic as it is about math.
We can paraphrase the question (a great thing to do with long word problems) as:
Now let''s apply some logic: x will always be either somewhere ahead of y or somewhere behind y. Is there a reason why he ...”



Stuart Kovinsky
posted a reply to Is 2^x greater than 100?
in the Data Sufficiency forum
“Hi!
We have a yes/no question, so if we can get a definite YES or a definite NO, we have sufficiency. If we get a maybe/sometimes/depends, we have insufficiency.
Looking at the stem, we think "we need to know about x".
(1) gives us an equation to solve for x. If we can solve for ...”



Stuart Kovinsky
posted a reply to Female employes in X
in the Data Sufficiency forum
“Hi!
Without any doubt, the most powerful concept for data sufficiency is "number of equations vs number of unknowns". You can use that rule (and its exceptions) to solve many DS questions without doing much, if any, math.
Let''s apply it to this particular question.
Step 1 of the ...”






Stuart Kovinsky
posted a reply to Usage of whom
in the Sentence Correction forum
“Hi!
A great way to determine whether to use "whom" or "who" is to turn the sentence into a question and answer it with "he" or "him".
For example, for (B) we''d ask "by whom were the mountains named?" We''d answer: "they were named by ...”



Stuart Kovinsky
posted a reply to Weighted Average Problem
in the Problem Solving forum
“Hi there!
My first post on the site for a while, but I can''t resist a good PM!
As Matt notes, your solution is 100% correct  a really important thing to remember about high level GMAT questions is there''s almost always an "angle" to solving them  and if you find the right one, ...”



Stacey Koprince
posted a reply to 2010  Best GMAT practice tests
in the GMAT Strategy forum
“Hi, guys, someone just pointed something out to me and I came here to correct a small piece of misinformation. It''s actually not the case that MGMAT CATs automatically give you something harder for the very next question when you get something right or easier when you get something wrong. We ...”



Stuart Kovinsky
posted a reply to Coordinate Geometry
in the Data Sufficiency forum
“We didn''t get lucky  the question was designed to reward people who saw the quick solution.
Most GMAT math questions are designed with 4 levels of reward:
1) negative reward, for people who spend time on it and get it wrong;
2) 0 reward, for people who recognize that they don''t know how to ...”



Stuart Kovinsky
posted a reply to applications
in the Data Sufficiency forum
“You''re 100% correct about the interpretation, but not about the confusion. We don''t know how deposits and acceptances relate to enrolments, which is why the statements, even combined, are insufficient.”



Stuart Kovinsky
posted a reply to Coordinate Geometry
in the Data Sufficiency forum
“Hi!
This question should take about 15 seconds if you actually draw out the xy plane. There are no bonus points on the GMAT for supercomplicated math, so avoid it whenever possible!
If you plot the 2 points, you can see that, since they have the same ycoordinate (3), one point that''s ...”



Stuart Kovinsky
posted a reply to applications
in the Data Sufficiency forum
“I don''t think that the problem with this question is that the language is confusing; rather, neither statement is relevant to the question, so we can very quickly say that the answer is (E).
The question asks what % of students who apply actually enrol. Neither (1) nor (2) mentions enrolment, ...”



Stuart Kovinsky
posted a reply to OG 13 #132
in the Data Sufficiency forum
“Hi!
Normally for this type of question we can rely on our old friend, "number of equations vs number of unknowns". However, there are some cases, such as this one, in which you have more info that you originally thought and you don''t actually need as many equations as you may think.
...”



Stuart Kovinsky
posted a reply to how do i solve this?
in the Problem Solving forum
“Great job!
Here''s a bit of clarification on solving this type of problem.
There are simple rules for multiplying exponents (x^a * x^b = x^(a+b)) and raising exponents to other exponents ((x^a)^b=x^(a*b)), but there''s no simple way to add or subtract exponents.
In fact, the only time you ...”



Stuart Kovinsky
posted a reply to manufacturing
in the Problem Solving forum
“Hi!
Like many GMAT questions, this one looks much more difficult than it actually is.
First, we can simplify by recognizing that the numbers on the right side are wholly irrelevant. The question would have an identical solution if the original equation were:
C = rst
Since that equation ...”



Stuart Kovinsky
posted a reply to revolutions
in the Problem Solving forum
“Hi!
You can solve this doing a lot of math, but any time you have variables in the choices, you can also pick numbers to solve  and picking numbers is often much easier than algebra. Let''s try it a couple of different ways!
Before we jump in, let''s make sure we identify exactly what the ...”



Stuart Kovinsky
posted a reply to cabbage
in the Problem Solving forum
“Hi!
As always, let''s start by identifying the exact question: what''s the gross profit?
Well, gross profit = total revenue  total cost. We''re given the total cost of $600, so we need to find the total revenue.
We''re told that 2/3 of the heads were sold for 25% above cost/head. There ...”



Stuart Kovinsky
posted a reply to OG 12 DS #89
in the Data Sufficiency forum
“Hi!
While you certainly can solve by manipulating equations, you can also solve with common sense and logic  very powerful tools on the GMAT that people often overlook.
We should be able to dismiss each statement by itself fairly quickly, since they each give us one relationship that''s not ...”



Stuart Kovinsky
posted a reply to Stats.. relationship among different pieces
in the Problem Solving forum
“1,3,5,5 is the same as 1,1,3,5
Similarly, 1,5,5,5 is the same as 1,1,1,5
The missing set is 1,1,5,5
On a side note, you will NEVER need to calculate SD on the GMAT (and, accordingly, you don''t need to know the SD formula)  you just might need to know what SD measures (how spread out are ...”



Stuart Kovinsky
posted a reply to median question..
in the Data Sufficiency forum
“Hi!
We''re told that 25% of projects have 4+ employees and 35% have 2 employees. Since the only number that doesn''t fall into "4 or more" and "2 or fewer" is 3, all of the remaining projects must have exactly 3 employees.”



Stuart Kovinsky
posted a reply to x/y<0?
in the Data Sufficiency forum
“Hi!
While this question illustrates some important concepts, it is 100% NOT a real GMAT question. What''s the source?
As TheCEO notes, statement (1) proves that the answer is "no" and statement (2) proves that the answer is "yes". On the GMAT, the two statements will ...”



Stuart Kovinsky
posted a reply to Martin's theory
in the Reading Comprehension forum
“Hi!
Let''s look right at the beginning of the passage:
Since the new research indicates that humans arrived "much earlier than 11,000 years ago", it directly attacks Martin''s theory that the arrival (i.e. not just the presence) of humans was responsible for the mass extinctions ...”









shovan85
posted a reply to concept of "OCTAVE " in RC
in the Reading Comprehension forum
“I don''t know if it is really helpful!! Unless you can recognize the Tone/Opinion of the passage this tool is least helpful. Anyways that''s just an opinion :)
Below is the link for OCTAVE  (Scroll the video to 1:11:08/2:36:48)
http://www.youtube.com/watch?v=9NApwEPHyOA
This is being taught ...”






shovan85
posted a reply to meteor stream
in the Reading Comprehension forum
“Choice A  the computer model confirmed the astronomers’ hypothesis that meteor
streams broaden with time, and although the model yielded an unexpected result, the passage does
not contrast the predictions yielded by competing theories.
Choice B  Best answer. The author describes the new ...”









shovan85
posted a reply to School Survey
in the Critical Reasoning forum
“Yes! And also, most students attend services for social reasons, and not religious reasons, that would seriously weaken the author''s argument.”



shovan85
posted a reply to In archaeology, as in the physical sciences
in the Reading Comprehension forum
“Easily discard B,C, and E.
IMO the main idea is in Green  it says about UNDERMINING the existing theories.
See the red highlight part in passage and Zeresenay Alemseged says about a finding in the history with some evidence. Honestly, I was confused between A and D, but marking each word of D ...”



shovan85
posted a reply to Scientists !!
in the Sentence Correction forum
“Subjunctive mood  Discard B and C
D and E  the scientists believe , however, the structure of these two says it is widely believed.
IMO A”



shovan85
posted a reply to Help Required !!
in the I just Beat The GMAT! forum
“Have a look at this awesome debrief!
http://www.beatthegmat.com/770q51v46ir8howaniitguycrackedthegmatt115958.html
Obviously you have no issues in Quant. Suggested books are there in the post. This member has mentioned all the Verbal books you need! Have a fresh start. Take a ...”



shovan85
posted a reply to School Survey
in the Critical Reasoning forum
“I understand this problem can be solved by POE. However, when you are dealing with Percentage and when you see strong words as MUST, you have to be cautious.
PERCENTAGE  You do not know how many students are in the religious service. For instance there were 1000 students in Total and Religious ...”



shovan85
posted a reply to School Survey
in the Critical Reasoning forum
“Left with A and D. As far as D is concerned, NOT ALL STUDENTS  that means with data from LESS students who attend the services, gives the survey a claim saying it''s decreasing the incidences of cheating! So, if the survey includes all students, that will STRENGTHEN the argument. D strengthens the ...”



shovan85
posted a reply to School Survey
in the Critical Reasoning forum
“If 15 years ago a stringent role has been applied, then how come cheating has decreased over last 10 years (Can have a look at the passage BOLD part). IMO C cannot be the answer.”



shovan85
posted a reply to clueless & confused
in the Sentence Correction forum
“I will be honest! I don''t remember any rule saying In parallelism, you cannot compare Singular to Plural Or Viceverse.
As both are available, I rule out Singular here so A, B, and D.
Among C and E, E has two issues: 1. "Condominium apartment owners" not parallel to "Owners of ...”



shovan85
posted a reply to problem of/in
in the Sentence Correction forum
“We cannot categorize this question as per "OF / IN". However, while managing something if you say "Problems of Managing..." then it means that the problems are outcome (sort of) of the managing of X. Whereas, when in you face problems during the management of X, then it can be ...”



shovan85
posted a reply to hurricane
in the Sentence Correction forum
“Please post all the options  Helps others as well!
The sentence says that the study is not practical. However, D says the tornado not making the study practical.”






shovan85
posted a reply to Sviatovin (OG13 49)
in the Critical Reasoning forum
“(A) No connection between the text timeline and this option  we are not talking about Prince!
(B) Accuracy of the report about Prince  nothing to do with the text.
(C) the diagram accurately represents the composition of Sviatov''s family at the time Sviatovin was written (Left out)
(D) We ...”



shovan85
posted a reply to Kiowi matriach, Aho
in the Sentence Correction forum
“For eliminating A, you can see the pronoun "They" is ambiguous, as it may refer to Home or it may refer to Festivals. As, home is singular we know that "they" points to "festivals"  but grammatically wrong. Consider, if those were homes instead of home.”



shovan85
posted a reply to As a part of their therapy
in the Sentence Correction forum
“practice falling during the 1950s as part of their therapy ....
Feels as if they were helped to practice falling at that period of time only. Practice falling during 1950s only not beyond that.
Clearly, distorts the intended meaning.”






shovan85
posted a reply to Sedan Holiday
in the Problem Solving forum
“Total Ways = Driver seat (2 ways) * 4 * 3 * 2 = 48 ways
Say the two sisters sit together S1 and S2
S1,S2 sequence possible ways = Driver seat (2 ways) * Next Front Seat (2 ways other parent and son) * Back remaining 1seat (2 ways son and other parent) * rest 2 back seats (1 way) = 8 ways
Now, ...”






Stuart Kovinsky
posted a reply to inequalities problem... again
in the Problem Solving forum
“As usual, Eagleeye provides a great explanation  using the number line is a great way to solve absolute value problems.
Another way to solve, especially when you have absolute value expressions on both sides of the equal sign, is to square both sides. Doing so generally leaves you with a ...”



Stuart Kovinsky
posted a reply to Adam Family
in the Problem Solving forum
“Hi!
You can solve this almost instantaneously if you understand what the question is asking.
Since each brother is double the weight of the previous brother, the correct answer has to be divisible by 2 many times. The only answer that has lots of factors is 2 is 64... choose E!
The ...”



Stuart Kovinsky
posted a reply to Problem Solving  Factorization Question??
in the Problem Solving forum
“Hi! This is an old question (and actually quite poorly constructed), but it illustrates a common feature in some GMAT questions, so it''s worth reviewing.
First, let''s break down the question:
Whenever you see this type of question, always rewrite it as:
n x 25 x 62 x 73/(5^2 * 3^3) = ...”



Stuart Kovinsky
posted a reply to Exponents problem
in the Problem Solving forum
“Let''s look at another approach we can take to the one posted by eagleeye.
First, a note of caution: when dealing with inequalities, be very wary of multiplying or dividing both sides by variables. Remember, if those variables turn out to be negative you have to reverse the inequality.
...”



Stuart Kovinsky
posted a reply to Geometry problems:
in the Problem Solving forum
“Using the vertical angle rule (opposite angles of intersecting lines are equal), we know that:
a=d
and
b=e
So, since a and b are complementary, d and e must also be complementary.
Further, since a=d, b and d are complementary; similarly, since b=e, a and e are complementary.
We know ...”



Stuart Kovinsky
posted a reply to Ratios problem
in the Problem Solving forum
“Hi!
A bit of theory before getting into the calculations.
First, when converting between linear, second order and third order equations (i.e. lengths, areas and volumes), you simply apply the proper exponent to find the new ratio.
For example, if comparing the areas of two squares with ...”



shovan85
posted a reply to CR weaken question
in the Critical Reasoning forum
“A  Do not know about the Participation of Citizen to achieve the target!
B  Left out  the answer.
C  The program is already profitable. Difficulty, costeffectiveness cannot come to picture!
D  Not concerned about pollution. Recycling is a PREFERABLE alternative which is demonstrated!
E  ...”



shovan85
posted a reply to diameter of the circle? (GMAT Prep 2)
in the Problem Solving forum
“Equilateral Triangle, AB = BC = CA, So, for the circle Arc AB = Arc BC = Arc CA
Arc ABC = Arc AB + Arc BC = 24. Thus, Arc Arc AB = 12 = Arc BC = Arc CA
So, perimeter of the circle = Arc AB + Arc BC + Arc CA = 3* 12 = 36 (as all Arc are same)
2*pie* radius = 36
=> radius = 36/(2*pie) = ...”






Stuart Kovinsky
posted a reply to Usage of HasExperts please help
in the Sentence Correction forum
“Hello!
"None of them have" and "none of them has" are both in common usage. While "none of them has" is technically "more correct", arguments can (and have!) been made for using "have" instead.
I can''t recall a GMAT question that required you ...”



Stuart Kovinsky
posted a reply to DS: Finding percents from averages
in the Data Sufficiency forum
“Hi!
Dimochka presents a great mathematical explanation, but let''s focus on efficiency, remembering one key rule:
To get the point on a DS question, you don''t need to actually answer the question  you just need to determine whether it''s possible to do so.
Keeping this rule in mind will ...”



Stuart Kovinsky
posted a reply to NEW ENTRY PROBLEMS
in the Problem Solving forum
“Hi!
If it''s actually a numeric entry question, then you have to enter the answer on the computer  it''s not multiple choice.
Again, these questions do NOT appear on the GMAT.”



Stuart Kovinsky
posted a reply to Integers x and y
in the Data Sufficiency forum
“Hi!
If x+2 and x+4 are between x and y, won''t x+1 and x+3 be between them as well?
You''re misinterpreting statement (2) as:
when in fact statement (2) simply tells us that there ARE 24 integers between x and y... period.
The only way this statement can be be true is if y = x + 25 ...”



Stuart Kovinsky
posted a reply to Primes
in the Data Sufficiency forum
“Hi!
Like a lot of data sufficiency questions, investing a bit of time in the question stem to understand what the question is really about makes working with the statements much simpler.
Let''s break down the stem:
What kind of positive numbers CANNOT be expressed as the product of two ...”



Stuart Kovinsky
posted a reply to NEW ENTRY PROBLEMS
in the Problem Solving forum
“Hi!
Is this a GRE question? There are no entry questions on the GMAT.
The first thing to note is that, on the GRE, you actually have access to a calculator. While you don''t need to use it (in fact it''s often quicker to solve multiple choice questions without a calculator), on the numeric ...”



Stuart Kovinsky
posted a reply to Problem solving  Ratio / Proportion
in the Problem Solving forum
“Hi!
As the other experts noted, this is a really tough math problem  which is why, almost certainly, the best way to approach it is strategically.
If you had provided answer choices (please always provide the choices!), we could have backsolved. When you have a very complicated word problem ...”



Stuart Kovinsky
posted a reply to OG 10th edition CRq174
in the Critical Reasoning forum
“Hi,
the question stem tells us to draw a conclusion "from the information given above". Two of those pieces of info are:
So, we do definitely know that the average age will increase over that time period.”



Stuart Kovinsky
posted a reply to really tough CR..
in the Critical Reasoning forum
“Hi!
For assumption questions, start by deconstructing the argument: identify the author''s conclusion and summarize the evidence.
Conclusion: the ONLY solution is to increase the number of government officials.
Evidence: old folk are underrepresented in the government, which sets policy ...”



Stuart Kovinsky
posted a reply to BOLD
in the Critical Reasoning forum
“Hi!
Bolded statement questions can be tricky, mostly because the answers often sound extremely similar. To avoid getting confused, rely on the most powerful tool for both RC and CR: making a prediction.
The best way to make a prediction on bolded statement questions is to roadmap the ...”



Stuart Kovinsky
posted a reply to I didn't even understand the question!
in the Problem Solving forum
“Hi!
A terminating decimal is one that ends, i.e. doesn''t infinitely repeat.
For example, 1.4, 8, 32.888991 and 27.6 are all terminating decimals.
Some fractions can be turned into terminating decimals, some can''t. For example, 1/3 is .33333 (going on forever). 1/5 is .2, which is ...”






Stuart Kovinsky
posted a reply to As part of a game, four people each must secretly
in the Problem Solving forum
“Here''s another way you can solve:
Prob = # desired outcomes/total number of possibilities
there are 4*4*4*4 = 256 total possibilities
Now on to desired outcomes!
The first person can pick any number, so she has 4 possibilities.
We want the second to be the same as the first, so she has ...”



Stuart Kovinsky
posted a reply to From new GMATprep Qn  Experts help please
in the Problem Solving forum
“Hi!
There''s a problem with the question  it doesn''t make sense as written (at least if the answer is supposed to be D).
You have Betty and William earning more than 50000, but then we never hear about William again. Then the question asks whether Wilma''s annual salary is greater than ...”






Stuart Kovinsky
posted a reply to Inequalities DS
in the Data Sufficiency forum
“Sure!
We want to know if the absolute value of a is greater than the absolute value of b. In other words, is the magnitude of a greater than the magnitude of b? (I.e. is a further from 0 on the number line than is b?)
As always, let''s start with the simpler of the two statements (that way if ...”



Stuart Kovinsky
posted a reply to Inequalities DS
in the Data Sufficiency forum
“Hi!
We want to know if the sum of x and y is positive. So, we either need the individual values of x and y or information about the expression "x+y".
(1) x  y > 0
We know nothing about x and y individually, so (1) is insufficient.
If the concepts don''t jump out at you, ...”



Stuart Kovinsky
posted a reply to Probability problem
in the Problem Solving forum
“That''s the exact rule!
If you just care about which objects to select, then you use the combinations formula.
If you care not only about which objects to select, but also the order of selection (or arrangement), then you use the permutations formula.
Here are two examples to illustrate the ...”



Stuart Kovinsky
posted a reply to the long advertisement
in the Critical Reasoning forum
“Hi! Just a reminder, please post the source of your questions (always a good habit).
Whenever you have an assumption family question (assumption/strengthen/weaken/flaw), start by deconstructing the argument: find the conclusion, summarize the evidence and identify the assumption.
Here, we ...”



Stuart Kovinsky
posted a reply to Probability problem
in the Problem Solving forum
“Just to elaborate a bit more, here''s the probability formula:
probability = (# of desired outcomes)/(total # of possibilities)
and, as Anurag noted, 36 was the total number of possible choices.
Whenever you''re doing a probability problem, starting out by writing that equation on your ...”



Stuart Kovinsky
posted a reply to Coordinate plane
in the Problem Solving forum
“Hi!
Let''s start with what''s probably the quickest approach: actually graphing the line.
The notepad that you get on the GMAT is graphlined, so it''s pretty easy to accurately draw out coordinate geometry questions. Accordingly, one option for solving this problem is to plot the two points, ...”



Stuart Kovinsky
posted a reply to Quadrilateral
in the Data Sufficiency forum
“Hi! It''s been a long time since I read this thread, but happy to reiterate a couple of key points.
First, and I can''t stress this enough: a square IS by definition a rectangle, since it has all the properties of a rectangle. The opposite is not true (i.e. a rectangle is not by definition a ...”



Stuart Kovinsky
posted a reply to Manhattan  weaken
in the Critical Reasoning forum
“Hello!
We''re asked to find the answer that would be cited by a SUPPORTER of the argument; in other words, we want to find the answer that, if true, would most STRENGTHEN the conclusion.
First, of course, we need to identify the conclusion. There are a number of tools we can use to do so: ...”



Stuart Kovinsky
posted a reply to Strengthen
in the Critical Reasoning forum
“Hi!
For strengthening questions, start by deconstructing the argument: find the conclusion, summarize the evidence and identify the author''s assumption. Next, make your prediction: the correct answer will support the assumption.
Let''s break down this argument:
Conclusion  TV ...”



Stuart Kovinsky
posted a reply to Assumption question quiet confusing...
in the Critical Reasoning forum
“Hi!
What''s the source of this question? It sounds a LOT more like an LSAT question than a GMAT one. If it''s from an LSAT source, then I''d advise that you completely ignore it, since the difference between sufficiency and necessity is rarely tested on the GMAT.
**FEEL FREE TO STOP READING ...”






Stuart Kovinsky
posted a reply to Something Wrong with the question???
in the Data Sufficiency forum
“Hi!
Remember  when inequalities and variables are involved, you have to be very careful with your manipulations!
You cannot simply crossmultiply by ab, since it''s possible that ab is negative. If ab IS negative, then when you cross multiply you get:
Is 1/(ab)<(ba)?
Is 1 > ...”



Stuart Kovinsky
posted a reply to stocks
in the Problem Solving forum
“Hi!
At first glance this may look like a permutations question, but it''s actually an exponent question with a tiny bit of permutations thrown in.
Since there''s no restriction on how many times we use each letter in each code, the number of possible 5 letter codes is simply 26^5 and the ...”



Stuart Kovinsky
posted a reply to households
in the Problem Solving forum
“Hi!
I played with the numbers a bit to maximize the duplicates, keeping in mind that I wanted to use as many of the DVDs, cell phones and MP3 players as possible twice.
I started with the MP3s, since that was the smallest group. Then I noted that there were 5 more Cell phones than DVDs, so I ...”



Stuart Kovinsky
posted a reply to three and four digit numbers
in the Problem Solving forum
“Hi!
Is there a reason why we couldn''t have x=170 and y=850?
In order for x+y to be a 4 digit number, at least one of the two must be greater than 500 (and the hundreds digits must sum to at least 9), but both don''t need to be greater than 500.
Fortunately, that issue doesn''t cause any ...”



Stuart Kovinsky
posted a reply to Counting Numbers 1
in the Problem Solving forum
“Hi!
Because you''re multiplying by a smaller number, you''ve actually removed those duplicates.
Here''s another way you could write the product:
(number of digits that could go in the first spot) * (number of digits that could go in the second spot that you haven''t used yet) * (number of ...”



Stuart Kovinsky
posted a reply to advanced gmat guide inequality
in the Data Sufficiency forum
“Hi!
The two statements aren''t identical, since for (2) a could be the negative root of a^2 and for (1) a is definitely nonnegative.
For example, for statement (1) we could pick a=4 and b=2 (since 4 = 2^2).
For statement (2) we could pick those same numbers (since 4^2 = 2^4), but we could ...”



Stuart Kovinsky
posted a reply to Consulting
in the Data Sufficiency forum
“Hi!
From the stem, we know that the fee is $x/hour for the first 100 hours and $y/hour for extra hours. We also know that Acme was charged a total of $14000. So, we can create the following formula:
100*$x + (n100)*$y = $14000
(n = total number of hours charged)
and the question is ...”



Stuart Kovinsky
posted a reply to Probability  Playing Cards
in the Problem Solving forum
“Hi! We want the probability of getting at least one matching pair. So, the only thing we don''t want to happen is 0 matching pairs. Accordingly, this is a great question on which to apply the "one minus" approach.
Remember this key formula for complex probability problems:
...”



Stuart Kovinsky
posted a reply to households
in the Problem Solving forum
“Hello!
First, a key strategy on min/max questions: whenever a question asks you to minimize one thing, maximize others; whenever a question asks you to maximize one thing, minimize others.
Next, let''s break this question down into two parts. First, the max number of households that has all ...”



Stuart Kovinsky
posted a reply to Sum of numbers
in the Problem Solving forum
“Hello!
On this type of question you always want to look for a pattern. In this case, let''s separate the units and tens digits.
Overall, we have 10 sets of numbers here: 09, 1019, 2029, ..., 9099.
In each set of 10, we have 1 of each units digit, so that''s 10 of each.
For each set ...”



Stuart Kovinsky
posted a reply to prime
in the Problem Solving forum
“Hi!
The wording of this question is a bit too ambiguous for the GMAT. Even though we can reason out what the question is supposed to say, you''ll never be put in that position on test day. What''s the source?
Better wording would have been:
Like many number property questions, we can ...”



Stuart Kovinsky
posted a reply to Coin flip questions made easy
in the GMAT Math forum
“Hi!
The formula is more complicated for die rolls because there are more than 2 possible outcomes, so "what you want" doesn''t equal "what you don''t want".
If you''re looking for one specific result, there''s a 1/6 chance of what you want and a 5/6 chance of what you ...”



Stuart Kovinsky
posted a reply to Problem Solving
in the Problem Solving forum
“Hi!
We see a fraction question with unknown values. Perfect time to pick numbers!
First, let''s identify the exact question: what fraction of UNSOLD cars were HYBRIDS. In other words, we want to solve for:
(# of unsold hybrids)/(total # of unsold cars)
To make the math work out, ...”



Stuart Kovinsky
posted a reply to 3 categories of workers
in the Problem Solving forum
“Hi again!
I strongly disagree  you will never have to make assumptions of this nature on the actual GMAT and doing so in practice will lead to habits on test day that could lead to fatal errors. For example, one of the most common DS mistakes is to assume facts that aren''t actually in ...”



Stuart Kovinsky
posted a reply to 3 categories of workers
in the Problem Solving forum
“Where do you see that information in the question stem?
Also, does a higher number in the ratio mean that a worker is more efficient or less efficient? For example, if you measure efficiency in tasks per hour, then higher is better; but if you measure efficiency in hours per task, then lower is ...”



Stuart Kovinsky
posted a reply to If 0<x<y, is yx < 0.00005
in the Data Sufficiency forum
“Sometimes brute force is the key to happiness on the GMAT.
(1) doesn''t give us any information about the upper boundary of y, so there''s no way it''s sufficient by itself: eliminate A and D.
(2) gives us an upper boundary on y AND we already know that x > 0, so it''s actually possible ...”



Stuart Kovinsky
posted a reply to 3 categories of workers
in the Problem Solving forum
“Hi!
This is a very poorly worded question and makes little sense. What does "the efficiency of the 3 categories of workers" mean? How is it related to wage? Nowhere does it say that different workers get different hourly rates (e.g. that hourly wages are proportional to efficiency, ...”



Stuart Kovinsky
posted a reply to Maths Problem
in the Problem Solving forum
“Hi!
Since p is a positive integer, p^3 is a perfect cube. Here''s an important rule about prime factoring of perfect squares, cubes, etc...:
perfect squares contain prime factors in pairs;
perfect cubes contain prime factors in triplets;
and so on...
For example:
36 is a perfect square; ...”



Stuart Kovinsky
posted a reply to Sets
in the Data Sufficiency forum
“Hi!
I can''t speak for all the experts here, but when I see a question linked in an image instead of typed in, I usually skip over replying (unless the image contains a diagram, which is a good excuse for attaching one).
The reason why I skip over these posts is because 90% of the time I''m ...”



Stuart Kovinsky
posted a reply to board of directors
in the Problem Solving forum
“A great opportunity to use logic instead of math!
There are 5 different people with whom Michael can be matched. There are 2 spots available on Michael''s team. Therefore, any one of the other 5 people will appear on 2/5 = 40% of Michael''s teams. Pick C!”



Stuart Kovinsky
posted a reply to Can someone please explain?
in the Problem Solving forum
“Hi!
We can set up a couple of simple equations to solve this relatively painlessly.
Let''s call his one way walking time "W" and his one way cycling time "C". We want to know the time for walking both ways, so we''re solving for 2W.
We know that:
W+C = 2h40min
...”



Stuart Kovinsky
posted a reply to perpendicular
in the Problem Solving forum
“Hi!
Although it may be somewhat timeconsuming, your best bet is to rewrite the equation in the stem and in each choice into standard y=mx+b form  that way you''ll be able to quickly compare the slopes.
Original:
3x + 4y = 8
4y = 3x  8
y = 3/4(x)  8
Slope = 3/4
Since ...”



Stuart Kovinsky
posted a reply to Probabilities
in the Problem Solving forum
“*TANGENT ALERT*
No math here, if you''re looking for math, move along!
There''s no need to put it directly before that (in fact, I challenge you to rewrite the sentence to put that where you want without causing a modification error in the remainder of the sentence)  the verb makes it clear ...”



Stuart Kovinsky
posted a reply to prime number
in the Data Sufficiency forum
“Hi!
Very open question, but we see it''s about primes. Whenever you see a DS question about primes, always think about 2, the only even prime!
Pretty straightforward question, so let''s dive right into the statements. (2) seems simpler, so let''s start there.
The only way that (2) could ...”



Stuart Kovinsky
posted a reply to Probabilities
in the Problem Solving forum
“Hi!
Because the sentence reads "that are", that must be referring to a plural subject; since "warehouse" is singular, it can''t be the referent of that.”



Stuart Kovinsky
posted a reply to Are x and y both positive?
in the Data Sufficiency forum
“Hi!
(2) says that x/y > 1
If you plug in x = 3/2 and y = 2, you get:
x/y = (3/2)/2 = (3/2)*(1/2) = 3/4 which is NOT greater than 1. Since your numbers don''t satisfy the statement, they''re impermissible and must be discarded.
As Aneesh aptly notes, you have to be VERY careful ...”






Stuart Kovinsky
posted a reply to If a, b, and c
in the Data Sufficiency forum
“Hi! Picking numbers is a great way to solve this (and many other) DS questions.
We quickly decide that (1) is insufficient, since it gives us no info about c. So, let''s eliminate A and D and jump to (2).
(2) ab>c
We can see that b is to the right of a on the number line, so let''s ...”



Stuart Kovinsky
posted a reply to Are x and y both positive?
in the Data Sufficiency forum
“Eagleeye gives a good math explanation; let''s look at the question purely using number properties concepts.
Q: are x and y BOTH positive.
(1) 2x2y=1
or
x  y = 1/2
Let''s think about what this means: on the number line, x is 1/2 to the right of y. Does that tell us anything about ...”



Stuart Kovinsky
posted a reply to Overlapping sets  OG12
in the Problem Solving forum
“Hi!
You''ve put 60 in the Brand A "total" column, which includes "brand A/brand B" and "brand A/not brand B". People in the "brand A/brand B" column are NOT "brand A ONLY"  they''re using both.
The 60 should go in the "brand a/not brand ...”



Stuart Kovinsky
posted a reply to Percentages
in the Problem Solving forum
“Hi!
I''m not sure where you''re getting these questions, but they, for the most part, suck. Each one only has 4 choices, they often have awkward or ambiguous language and test concepts far beyond (and irrelevant to) the GMAT.
If you''re actually studying for the GMAT, I''d avoid this source ...”



Stuart Kovinsky
posted a reply to Six digit numbers
in the Problem Solving forum
“Only 4 answer choices, so clearly this isn''t a real GMAT question  please always post your source we know if it''s relevant to the GMAT!
This question is a far more complicated version of a question that may appear on the GMAT, so it''s worth discussing. Once you understand how one of these ...”



Stuart Kovinsky
posted a reply to Another good evaluate question...
in the Critical Reasoning forum
“But what does "coming second" mean?
If the Bible got 999 votes and 1984 got 1 vote, then 1984 came second; if the Bible got 501 votes and 1984 got 499 votes, then 1984 came second. Do both scenarios make us think that 1984 actually affected a lot of people''s lives?”



Stuart Kovinsky
posted a reply to jury
in the Problem Solving forum
“Hi!
I gave a detailed explanation to this question here:
http://www.beatthegmat.com/isuckatprobabilityneeddesperatehelpt8927.html”



Stuart Kovinsky
posted a reply to Inequalities OG12 #38
in the Problem Solving forum
“Hi!
When you''re not sure what to do with the algebra, don''t waste your valuable test time trying to figure it out. Instead, dive right in and pick numbers.
As you noted, each statement must be insufficient alone, since each one only provides 1/2 the picture. So, let''s jump right to ...”



Stuart Kovinsky
posted a reply to Another good evaluate question...
in the Critical Reasoning forum
“Hi!
Relevant information questions are really scope questions  we want the answer that''s most inside the scope of the issue. These questions belong to the assumption family.
A great approach is to break down the argument just as you would for any assumption/str/wkn question: find the ...”



Stuart Kovinsky
posted a reply to Couldn't get the problem
in the Problem Solving forum
“Hi! Wacky symbol questions appear from time to time on the GMAT; these questions almost always resolve to simple substitution.
Of course, before you can substitute you have to understand the question. So, the key to solving these problems is to take the time you need to break down the question ...”



Stuart Kovinsky
posted a reply to Confusing Probability
in the Problem Solving forum
“Hi!
Part of you''re analysis is 100% correct: for any given string of 7 coin flips, there''s a (1/2)^7 chance of it happening.
For example, there''s a (1/2)^7 probability of getting:
HHHHHHH; or
HHHHHHT; or
HHHHHTT; and so on...
However, here''s the problem: to satisfy what the ...”



Stuart Kovinsky
posted a reply to weighted averages
in the GMAT Math forum
“Here''s a very useful rule to remember for data sufficiency:
In order to find the actual value of a quantity, you need at least one actual quantity somewhere in the information.
For example, if all you''re given is a ratio, there''s no way to determine the actual quantities involved; ...”



Stuart Kovinsky
posted a reply to Confusing Probability
in the Problem Solving forum
“Hi!
We can definitely solve using the coin flip formula and adding up the probability of each scenario that we want. However, we can solve MUCH quicker using logic.
We want all the cases with an even number of heads. So, we want:
0H
2H
4H
6h
We DON''T want all the cases with an odd ...”






Stuart Kovinsky
posted a reply to How to plug in for this? Official GMAC Hard
in the Problem Solving forum
“Hi! First, let''s make sure we understand the essence of the question  since we''re increasing by a set percent each year, what we really have here is a compound interest problem. The problem basically boils down to:
Principle investment on Jan 1, 1992: $k
interest rate per year: c%
total ...”






Stuart Kovinsky
posted a reply to remainder problem
in the Problem Solving forum
“Hi!
Picking numbers is a great approach to solving many number property questions.
Here, our constraints are that n/9 must have a remainder of 8 and n must be even. What''s the smallest number that satisfies these constraints? n=8 (8/9 has a quotient of 0 and a remainder of 8).
Now let''s ...”



Stuart Kovinsky
posted a reply to abc
in the Problem Solving forum
“Hi, those will indeed have different results, but since 6/2 doesn''t satisfy the condition that ab^2/c is even, we can ignore that possibility.
Remember, we take the equation in the question stem as a given; accepting that the equation is true, we now check to see which statement MUST also be ...”



Stuart Kovinsky
posted a reply to Single eqn solving??
in the Problem Solving forum
“Hi!
We can solve this question superduper quickly via backsolving. Since we want the minimum number of copper coins, let''s start with the smallest answer, (E).
(E) 0 copper means $2.80 from brass  since 280 is not a multiple of 25, wrong!
(D) 1 copper means $2.60 from brass  since 260 ...”






Stuart Kovinsky
posted a reply to Remainder R
in the Data Sufficiency forum
“Picking numbers is a very efficient way to solve number property DS questions.
From the question stem, we know that (4+7n)/3 has a remainder of r; we want to know that value. What do we need? Information about n.
1) n+1 is a multiple of 3.
If n=2 (we''re allowed to pick 2 since 2+1 is a ...”



Stuart Kovinsky
posted a reply to Sets problem
in the Data Sufficiency forum
“Let''s solve using the most powerful rule for data sufficiency: number of equations vs number of unknowns.
First, picture (sorry, I''m not good at computer diagrams!) a Venn diagram with 3 circles. There are 7 different sections: Only R, only S, only T, RS overlap, RT overlap, ST overlap, RST ...”



Stuart Kovinsky
posted a reply to usage of will and would
in the Sentence Correction forum
“For the first one I''d say "there is hope that the economy will grow". You would only use "would grow" if you''re adding a "but" to the end. For example, "I had hoped that the economy would grow, but it shrunk." (Or "I hoped that the economy would grow, ...”



Stuart Kovinsky
posted a reply to Confused  Any Ideas
in the Problem Solving forum
“From the question stem, we know that n is an integer. Accordingly, we know that sqrt(3+x) is an integer. What numbers have roots that are integers? Perfect squares.
Consequently, (3+x) must be a perfect square, i.e. 1, 4, 9, 16, 25, 36, ...
Now we just need to plug in each answer to see ...”



Stuart Kovinsky
posted a reply to usage of will and would
in the Sentence Correction forum
“Hi,
would is NOT the past tense of will. Would is used in conditionals, e.g. "I would go to Harvard if I were to get an 800 on my GMAT".
Would can be used in different tenses. For example:
I would have gone to Harvard if I had gotten an 800 on my GMAT.
"Will" ...”



Stuart Kovinsky
posted a reply to function h(n) number properties
in the Problem Solving forum
“Here''s the takeaway: if h(100) is divisible by every prime from 1 to 50, then h(100)+1 CANNOT be a multiple of any of those numbers.
What Bill was saying is that the greatest common factor of any TWO consecutive integers is 1. Since h(100) and h(100)+1 are consecutive integers, then any prime ...”



Stuart Kovinsky
posted a reply to Airline Fleet  GMAT Prep
in the Problem Solving forum
“You can think of it that way, but you have to count the actual number of years starting from the beginning of 1980. I guess technically you''d hit your target 8 years and 364 days after you start, but that''s still 9 years, not 8. (If you start on Jan 1st 1980, you have your 9th change on Dec 31st ...”



Stuart Kovinsky
posted a reply to numbers 2
in the Problem Solving forum
“Hi,
I''m happy to explain the concepts, but first it''s important to note that the wording of both questions is definitely NOT what you''d see on the GMAT. Also, there are only 4 answer choices and, of course, on the real GMAT there will be 5. Please always post the source of your questions so ...”



Stuart Kovinsky
posted a reply to Airline Fleet  GMAT Prep
in the Problem Solving forum
“Hi! You could solve this question very quickly by brute force  just make a chart and keep track of what happens each year. Remember, on the GMAT you get points for picking the right answer, not for HOW you arrive at that answer. Sometimes brute force is quicker than algebra.
Year A planes ...”



Stuart Kovinsky
posted a reply to OG 13 #229 How many of the integers...
in the Problem Solving forum
“Here''s the #1 thing to remember when using the OG: it''s a great source of questions, but a horrible source of explanations. Especially for math, OG explanations are rarely the most efficient way to solve problems.
Since the biggest answer given is 5, plug ''n play is a great alternative way ...”



Stuart Kovinsky
posted a reply to if b < 1 and 2x  b = 0
in the Problem Solving forum
“Hi! Like many GMAT questions, we should start by simplifying the question itself.
We know that b < 1 and that 2xb=0. We can rewrite the equation as:
2x = b
Putting the two statements together:
2x = b < 1
2x < 1
x < 1/2
Now we need to find the answer that MUST be true, ...”



Stuart Kovinsky
posted a reply to Probability of cars
in the Problem Solving forum
“Hi!
Lots of good solutions already posted, so I''m just going to focus on your actual question.
When we made the calculation to get 192, we were working on the basis that order DID matter. If you think about those possibilities, you''ll see that we''ve over counted.
For example, if the ...”



Stuart Kovinsky
posted a reply to Thought process on remainders
in the Problem Solving forum
“Hi,
for the GMAT, your goal is to be as efficient as possible. While you could certainly derive a fancy formula to solve this type of problem, brute force is almost certainly quicker.
Since we want all the numbers that leave a remainder of 1 when divided into 16, what we really want is the ...”



Stuart Kovinsky
posted a reply to Quadratic Equation
in the Data Sufficiency forum
“Hi!
There are two problems with your analysis, one of which may just have been a typo.
First, the minor issue: (C) is correct if you require both statements in combination; based on the rest of your post, I''m going to assume that you meant that you thought the correct answer should be (D), ...”



Stuart Kovinsky
posted a reply to Challengestatistics
in the Data Sufficiency forum
“Hi!
You seem to have misinterpreted the question as "what is the smallest possible number in the set?", when in fact it''s simply "what is the smallest number in the set?"
With (1) alone, there''s no way to determine the actual value of x, y or z, so (1) is insufficient.
...”



Stuart Kovinsky
posted a reply to Angles
in the Problem Solving forum
“Hi!
You''d definitely benefit from drawing out a clock on this question (as you would on pretty much any geometry question). Sadly, computergenerating diagrams is not one of my strengths, so we''ll just visualize.
Let''s think about where the hands are at 4:20: the little hand is on the 4 ...”






Stuart Kovinsky
posted a reply to Confusion with wording of option (2) ?
in the Data Sufficiency forum
“Hi,
the key word is "any".
(2) says that the difference between ANY two factors of n is odd; read ANY as EVERY (they mean the same thing).
So, if n=12, then we have lots of pairs of factors that do NOT have an odd difference, e.g.:
31=2
42=2
62=4
and so on...
The ...”









Stuart Kovinsky
posted a reply to Combinations Problem
in the Problem Solving forum
“Hi!
Let''s start with Step 1 of the Kaplan Method for PS: analyzing the question stem.
We''re told that there are 2 different sizes of pad  let''s call them small and large ("s" and "l"). There are also 4 different colours, b, g, y and p.
We''re allowed to make 2 ...”



Stuart Kovinsky
posted a reply to Confusion with wording of option (2) ?
in the Data Sufficiency forum
“Hi! As Sanju points out, 62 is, in fact even; as is 31, another pair of factors of 6.
Let''s think about statement (2) some more. How do we get an odd difference between integers? If one is even and one is odd.
So, if a number has two odd factors, then we''ll get an even difference. If a ...”



Stuart Kovinsky
posted a reply to Confusion with wording of option (2) ?
in the Data Sufficiency forum
“Hi!
There''s nothing ambiguous about (2), it just needs to be read carefully (like all DS statements!).
"The difference between ANY two distinct positive factors of n is odd" must mean two things:
1) n only has 2 distinct factors; and
2) those 2 factors are 1 apart.
The first ...”









Stuart Kovinsky
posted a reply to Source Grockit: DS: Inequallity
in the Data Sufficiency forum
“Hi!
Whenever you see inequalities and variables, alarm bells should go off in your head and your internal warning system should be shouting "DANGER DANGER DANGER!!!"
Remember this key difference between equations and inequalities:
When you multiply or divide both sides of an ...”



Stuart Kovinsky
posted a reply to Greensboro County, 75 people
in the Problem Solving forum
“Approaching a different way we also see that the question is defective.
Let''s call those who own both "b" and those who own neither "n". So, we have:
(1) b + n = 1/2(75+35b)
(we subtract the extra b because we want "the amount [which should be "the ...”



Stuart Kovinsky
posted a reply to Combination Problem : Need Help
in the Problem Solving forum
“Hi!
The question is actually much easier than you think. Let''s start with a simpler version of the same question:
Solving by brute force, we get:
Salad/Fish
Salad/Chicken
Salad/Beef
Soup/Fish
Soup/Chicken
Soup/Beef
for a total of 6 possible meals.
However, what we''re ...”



Stuart Kovinsky
posted a reply to Zanco's failure
in the Critical Reasoning forum
“If you add the "who patronize Zanco aren''t likely" as you have, then that answer would definitely be a strengthener, since it''s more evidence to support the conclusion.
However, a strengthener isn''t necessarily an assumption; for that same reason, if the denial of your choice ...”



Stuart Kovinsky
posted a reply to Zanco's failure
in the Critical Reasoning forum
“Hi again!
Your denial of (3) is spot on (some people forget that the opposite of "all don''t" is "at least one does"), but I disagree that the denial actually weakens the argument.
Just because 1 person does, in fact, use moral considerations doesn''t make us believe that ...”



Stuart Kovinsky
posted a reply to Players in a tournament
in the Problem Solving forum
“Hi!
We have variables in the choices, so we can definitely pick numbers to solve this problem.
Let''s pick the smallest numbers we can to keep the question manageable: 6 teams and 4 players per team.
Now let''s write out our teams, in accordance with the rules:
1: ABCD
2: DEFG
3: ...”



Stuart Kovinsky
posted a reply to Probability Strategy
in the Problem Solving forum
“Hi!
Both solutions are always correct  if you get two different answers, then you must have made a mistake along the way.
Here, for example, you''ve miscalculated what you call solution B.
In your solution, you only look at the case in which none of them is a 6; however, we also satisfy ...”



Stuart Kovinsky
posted a reply to Zanco's failure
in the Critical Reasoning forum
“As noted above, an assumption is something that MUST be true in order for the conclusion to follow from the evidence. Accordingly, the strength of an assumption must match the strength of the argument.
For this reason, avoid EXTREME answers on assumption questions. For this argument to hold, ...”



Stuart Kovinsky
posted a reply to Zanco's failure
in the Critical Reasoning forum
“Hi!
An assumption is something that MUST be true in order for the conclusion to follow logically from the evidence. In other words, a conclusion is a missing but necessary piece of evidence.
The classic way to identify an assumption is to look for a disconnect, i.e. mismatched terms. This ...”



Stuart Kovinsky
posted a reply to Main Point  MGMT cat 1
in the Critical Reasoning forum
“Hi!
Step 1 of the Kaplan Method for CR: identify the question type
A large part of the problem here is that people have misidentified the question; it is NOT asking us to draw an inference. Rather, it''s asking for the main point, or the conclusion of the argument.
Remember: an inference ...”



Stuart Kovinsky
posted a reply to P is a polygon
in the Data Sufficiency forum
“Umm.. not to be too picky, but the angles in your hexagon are NOT all equal (the 2 angles of the "pointy bits" are different from the other 4 angles).
Any polygon with equal angles is, in fact, cyclical.”






Stuart Kovinsky
posted a reply to Probability problem
in the Problem Solving forum
“Hi!
As always, when a common formula applies you should jot it down on your scratch paper. So:
probability = # of desired outcomes/total # of possibilities.
Total # of possibilities is simply the number of numbers, which is 450 (to count the number of consecutive integers in a set, take:
...”



Stuart Kovinsky
posted a reply to Venn diagrams and Matrices
in the Problem Solving forum
“As Ron said, for 2set questions, you can use either approach (or the overlapping set formula:
True # of objects = total # in group 1 + total # in group 2 + total # in neither group + number in both groups).
If you''re getting different answers using different approaches, then you''re making ...”



Stuart Kovinsky
posted a reply to Can anyone help me figure this one out?
in the Problem Solving forum
“Perfect solution, just to clarify a few steps:
3x = sqrt(3)*(x^2)/4
We know that x is positive (since it''s the side of a triangle), so we can safely divide both sides by x to get:
3 = sqrt3 * x/4
Multiplying both sides by 4:
12 = sqrt 3 * x
Dividing both sides by sqrt3:
...”



Stuart Kovinsky
posted a reply to GMAT Prep DS problem
in the Data Sufficiency forum
“Hi!
We''re not assuming anything (never assume in DS!)  we''re intentionally looking at the most extreme case to see if it''s possible to get a "NO" answer to the question.
If Bob overestimates some books, then he''d be under by even less than our extreme possibility, pushing him ...”



Stuart Kovinsky
posted a reply to Fast way to do this?
in the Data Sufficiency forum
“You can use your knowledge of concepts to solve rather than plugging in numbers (although picking numbers is also a great way to go).
First, let''s ask ourselves when we''ll get a YES answer to the question.
First, we need the sign of the top and bottom to be the same (if the signs were ...”



Stuart Kovinsky
posted a reply to Carol's Bday
in the Data Sufficiency forum
“Ooo, great question, since it gives us the opportunity to apply the most powerful rule known to DS experts across the universe: number of equations vs number of unknowns.
Here''s the rule:
To solve for a system of n variables, one requires n distinct linear equations.
Or, somewhat ...”



Stuart Kovinsky
posted a reply to GMAT Prep DS problem
in the Data Sufficiency forum
“Hi!
Bob certainly wouldn''t make it very far in the accounting world (although I think he may have worked for Enron).
Let''s start with Step 1 of the Kaplan Method for DS: Analyze the question stem.
We know that Bob rounds off book prices to the nearest dollar and want to know if "the ...”



Stuart Kovinsky
posted a reply to DS: number properties
in the Data Sufficiency forum
“We know that:
x^n  x^(n) = 0
or
x^n = x^(n)
and we want to find the value for x.
Let''s start by analyzing the question stem, something too many test takers fail to do.
A negative exponent is the same as 1 over that exponent. In other words:
x^(n) = 1/(x^n)
So, we can ...”






Stuart Kovinsky
posted a reply to Manufacturing DS
in the Data Sufficiency forum
“I just want to address this particular concern, since it''s a great question.
Whenever you have a term of two variables multiplied together, you no longer have a linear equation (since when you sub in for x or y, you''ll get a squared term).
For example, let''s look at this question:
...”



Stuart Kovinsky
posted a reply to x=the 12th power of an integer?
in the Data Sufficiency forum
“Common sense and logic are some of the most underrated GMAT tools; applying "math common sense" to this problem makes it understandable.
Let''s agree that neither statement on its own is sufficient and jump right to combination.
Since x > 1, we know that statements (1) and (2) ...”



Stuart Kovinsky
posted a reply to Two models of computers
in the Problem Solving forum
“Some good solutions posted already; we can also use the basic work formula for two workers:
CT = combined time
A = time for worker 1 to do job on its own
B = time for worker 2 to do job on its own
CT = (A*B)/(A+B)
In this case:
CT = 9*18/(9+18) = 162/27 = 6
Since it takes 6 minutes ...”



Stuart Kovinsky
posted a reply to How to solve this the nondifferentiation way?
in the Problem Solving forum
“Although we don''t normally do so when there are variables in the choices, you can also solve by backsolving.
Let''s start by subbing in for B to get:
(x  A)^2 + (x  (A + 4))^2
= (x  A)^2 + (x  A  4)^2
If we Sub in x = A, we get:
(A  A)^2 + (A  A  4)^2
= 0 + 16
Now let''s ...”



Stuart Kovinsky
posted a reply to median question..
in the Data Sufficiency forum
“Hi!
When you have an even number of terms, the median is the average of the two middle terms.
Since there are 14 terms in your set, we want the average of the 7th and 8th terms. Since T7 and T8 are both 3, the average is:
(3+3)/2 = 6/2 = 3
and, accordingly, the median is still 3.”



Stuart Kovinsky
posted a reply to GMAT PREP PS Problem
in the Problem Solving forum
“Hi Alex!
This question has been posted and explained many times. If you do a search on "circle intersect triangle" you''ll find a number of detailed solutions, many of which have very informative diagrams.
Happy hunting!”



Stuart Kovinsky
posted a reply to GMAT PREP PS Problem
in the Problem Solving forum
“Excellent solution!
My only advice would be to use fractions instead of decimals to minimize the calculations.
If x = 4/5(y), then y = 5/4(x)
(it''s always just the reciprocal of the fraction on this type of question)
and we can quickly convert 5/4(x) to 1.25(x), since the answers are in ...”



Stuart Kovinsky
posted a reply to Probability Inquiry
in the Problem Solving forum
“Hi Ray,
I''m not a big fan of the P(A) + P(B)  P(A&B) approach, since as you point out it can get confusing in more complicated situations. If you''re comfortable with the other approaches, I''m not sure why you''d ever use this one.
That said, and since you seek understanding (always a ...”






Stuart Kovinsky
posted a reply to GMAT PREP PS question
in the Problem Solving forum
“Hi!
This question is testing you on the "length of a side of a triangle rule":
each side must be greater than the positive difference between the other two sides and less than the sum of the other two sides, or, if we call the sides x, y and z:
yz < x < y + z
Applying ...”



Stuart Kovinsky
posted a reply to PS: %
in the Problem Solving forum
“Hi!
Almost certainly, the quickest way to solve this type of weighted average problem is by plotting the groups and the total on a number line, like this:
Group 1 x Total Avg y Group 2
in which x and y represent the distance between Group 1 and the average and Group 2 ...”



Stuart Kovinsky
posted a reply to Rule of 70 question
in the Problem Solving forum
“Hi!
Since the employee is 32 at the start of her employment, she needs to accumulate 7032 = 38 "points" to retire.
Each year she works she gets 2 points  1 for working and 1 for getting a year older. So, to determine how many years she needs to work, we simply divide 38 by 2 to ...”



Stuart Kovinsky
posted a reply to Kaplan:CPR
in the Critical Reasoning forum
“We''ve identified that we have a weakening question, so let''s go to step 2 of the Kaplan method for CR: untangle the stimulus.
First, it''s essential to identify the restaurateur''s conclusion  I think that part of the problem has been that people haven''t properly figured out what the main ...”



Stuart Kovinsky
posted a reply to Standard Deviation in DS
in the Data Sufficiency forum
“On the GMAT, one is NEVER asked to calculate the SD of a set. However, one might be asked, as in this question, whether it''s POSSIBLE to calculate the SD of a set.
In order to determine the SD of a set, you need 2 pieces of information about the set:
1) the number of terms; and
2) the exact ...”



Stuart Kovinsky
posted a reply to PR 1024 Functions #6
in the Data Sufficiency forum
“Hi!
The question makes no sense as you''ve posted it. Unfortunately, p164 is omitted from that preview of the book, so there''s no way to check the actual question.
Here''s how the question likely reads in order for (D) to be correct:
If f(x) = x^2 + x for all values of x, what''s f(y)?
...”



Stuart Kovinsky
posted a reply to Inequalities with Absolute value
in the Problem Solving forum
“Hello!
If a does in fact equal 1.75, then of course 1.75 < 2 and (I) must be true. Are you sure that you''ve accurately reproduced the question/answers?
We can solve very quickly just by plugging in a=1.75 to each statement:
(I) 1.75<2... Is 1.75 < 2? YES, therefore TRUE
...”



Stuart Kovinsky
posted a reply to probability.
in the Problem Solving forum
“Hello!
This is a nonGMAT question for 2 reasons. First, there are no answer choices. Second, GMAT probability always deals with INDEPENDENT events  here, not only does the question not specify that the events are independent, but it also implies that they could be dependant. After all, if ...”



Stuart Kovinsky
posted a reply to probability.
in the Problem Solving forum
“Hello!
I see that you''re fairly new to the forums, so just a friendly tip  please post your questions in the right place! This is the problem solving forum, but this is a data sufficiency question.
Data sufficiency is a test of your knowledge of concepts, NOT your ability to do lots and ...”






Stuart Kovinsky
posted a reply to Word Problem: Kaplan WB
in the Problem Solving forum
“Hi!
It doesn''t say that he used all of his bills, just that he received no change from the purchase. In other words, he couldn''t have bought an item that cost $8, because then he would have received at least $2 in change.
For example, if you walked into a store with $200 in your wallet, ...”



Stacey Koprince
posted a reply to Neanderthals had a vocal tract
in the Sentence Correction forum
“I don''t post on the forums any longer but will answer this one quickly. :)
B is the official answer.
E is incorrect because it has a pronoun issue: the subject of the first clause is "vocal tracts" and the "they" pronoun later in the sentence is also a subject pronoun, ...”



Stuart Kovinsky
posted a reply to King Alfred
in the Sentence Correction forum
“As always, great explanation by Ron!
Another reason we can eliminate (A) is improper verb tense. In the nonunderlined portion of the sentence we have the simple past used to refer to an action taken in 893. Since the action in the first part of the sentence refers to 886, it should use an ...”






Stuart Kovinsky
posted a reply to Eating contest
in the Problem Solving forum
“Here''s a good rule to remember for the GMAT:
When a question asks you to minimize one thing, you want to maximize something else; when a question asks you to maximize one thing, you want to minimize something else.
Here we''re asked to minimize the number of people who eat all 3 meals; to ...”



Stuart Kovinsky
posted a reply to Modulus PS
in the Problem Solving forum
“We can solve this problem by picking numbers to eliminate 4 of the 5 choices.
First, let''s pick a big positive number. If x=10, we get:
10/10 < 10,
which is certainly true. Therefore, x could be 10. Accordingly, we can eliminate (c) and (d).
We can now either pick another number ...”



Stuart Kovinsky
posted a reply to Coin flip questions made easy
in the GMAT Math forum
“That question asks you to solve for the standard deviation of a set; since the GMAT never asks you to solve for standard deviation, I have no idea why anyone would even want to solve that problem!”






Stuart Kovinsky
posted a reply to Rivaling the pyramids of Egypt Modifier Issue
in the Sentence Correction forum
“Hi!
B makes the same mistake as do C, D and E  they all have a giant misplaced modifier. If you recognize that issue (and it''s one of the "big 5" grammar issues tested on the GMAT, so you need to be a Master of Modification by test day), then this becomes a 1530 second question.
...”



Stuart Kovinsky
posted a reply to vinegar and water
in the Data Sufficiency forum
“Hi!
This question is a great illustration of the most powerful rule to remember for data sufficiency: number of equations vs number of unknowns.
Here''s the "official" wording of the rule:
Put more simply, if you have the same number of linear equations as you have variables, ...”



shovan85
posted a reply to MArx
in the Critical Reasoning forum
“Consider that, you do not know who is Marx (if he is a German or Not) and you do not know what is the base for someone to be idealist. Now see between the two options you are getting confused with. I guess you can Infer the correct option now :)”



Stacey Koprince
posted a reply to MEaning based SC. !
in the Sentence Correction forum
“Someone asked me to weigh in on this  I don''t normally post on the forums, but I will on this one. :)
Brian is absolutely right that the directions make no mention of needing to preserve the original meaning (and, of course, sometimes the original meaning is actually illogical or ambiguous and ...”



Stacey Koprince
posted a new topic called More news from GMAC on idioms
in the GMAT Strategy forum
“Hi, all
I just posted this in the comments section of my article, but it''s important enough that I wanted to add it here. Larry just emailed me again about the idioms issue.
Two very important things (the first from Larry, the second from me):
(1) Larry just got back into the office and ...”



Stacey Koprince
posted a new topic called GMATPrep for the Mac
in the GMAT Strategy forum
“Hey, all, one other little tidbit I wanted to share from the GMAC conference  they''re (finally!) going to come out with a version of GMATPrep for the Mac!
It won''t, however, be until the next version of GMATPrep launches, in April of 2012. So  no real news for people taking the test before ...”



Stuart Kovinsky
posted a reply to GUESS
in the Problem Solving forum
“Hi!
This is a very strange question  did you make it up? You''ll never see something in this format on the GMAT.
First, answer (D) makes no sense  points cannot be parallel (the concept of parallelism doesn''t apply to points). Similarly with (E)  what does "on different ...”



shovan85
posted a reply to Account
in the Sentence Correction forum
“Its E. E is not only stating the correct meaning (Using....) but also it is concise (in both x and y). There is a great video tutorial by Ron Purewal available in the below link...
http://www.manhattangmat.com/thursdayswithron.cfm
Scroll to Sep 23 2010.”






shovan85
posted a reply to Area
in the Problem Solving forum
“The center is at (0,6). The circle formed around this center has to be symmetrical against the Yaxis.
The distance between the two points intersecting Xaxis is 16. So, we can say the length of the chord is 16.
The distance of any of the points from origin (0,0) is 8 as the circle is ...”



Stacey Koprince
posted a reply to MGMAT Problem (Advanced Quant)
in the Data Sufficiency forum
“Yes, we definitely keep track so that we can fix errors in future printings, and we also post errata lists online so that you can check to see whether something is already a known error. I don''t think we have an errata list up for this book yet, but we will soon.
If you spot errors in any of our ...”



Stuart Kovinsky
posted a reply to Average Speed of Bus
in the Data Sufficiency forum
“Hi,
you can''t use that approach on this question, since it involves assuming facts that aren''t in evidence.
From (1) we can conclude that for the first half of the time, the average rate is 50 mph.
From (2) we can conclude that the rate for the first half of the distance is two times the ...”



Stuart Kovinsky
posted a reply to Box office receipts
in the Critical Reasoning forum
“Hi,
"box office receipts" always refers to revenue (at least in North American colloquial English, which is what the GMAT uses). As Mitch points out, if it referred to the number of movies then the stimulus is selfcontradictory, which can never happen on inference questions.”



Stuart Kovinsky
posted a reply to At a certain company
in the Data Sufficiency forum
“Hi,
there''s no need for the original question to mention that, because it''s implied by default. If the question maker wanted there to be no people who belong to the "neither" category, then THAT would have had to be explicitly stated.
For example, if you were to say:
"some ...”



Stuart Kovinsky
posted a reply to PROBLEM SOLVING
in the Problem Solving forum
“Hi!
The GMAT is in part about math, but it''s also in part about speed. Without any doubt the quickest way to solve this problem, and many problems in which you''re given rules about how variables behave but no actual values, is by picking numbers.
m/6 has rem 2, so let''s pick m=8
n/6 has ...”



Stuart Kovinsky
posted a reply to Sets sum
in the Problem Solving forum
“Many of the questions with which you''re practicing have been previously discussed on this board. The BTG search tool is very useful.
Here are a couple of threads discussing this question:
edit: typo!”



Stuart Kovinsky
posted a reply to Earth
in the Critical Reasoning forum
“Why do you think B must be true in order for the conclusion to follow? If you post your reasoning, we can give you a better answer.
There are two general reasons why B isn''t an assumption.
First, it''s too extreme. Does every river on earth have to have roughly the same level of salt for ...”






Stuart Kovinsky
posted a reply to circumf of circle
in the Problem Solving forum
“Great solution!
A lesser known formula for the area of a square is:
area = (diagonal^2)/2
which is derived from the Pythagorean theorem (using 45/45/90 ratios).”



Stuart Kovinsky
posted a reply to triangles
in the Problem Solving forum
“Hi,
here''s a link to another post with pretty diagrams:
[url]http://www.beatthegmat.com/numberofpointsacirclecanintersectatrianglet76683.html[/url]
If you search "circle intersect triangle" onsite you''ll find a number of threads discussing this question.”



Stuart Kovinsky
posted a reply to integers
in the Problem Solving forum
“Hi Divya,
while I appreciate your enthusiasm for getting your questions posted as quickly as possible, I''m sure that I speak for all BTG users when I say we''d appreciate it even more if you''d slow down a bit and proofread your posts  there are so many typos and abbreviations that it''s almost ...”



Stuart Kovinsky
posted a reply to Anybody  Shortest/fastest way to solve this one?
in the Problem Solving forum
“Hi,
just because it''s true that the mean=median for all arithmetic progressions doesn''t mean that it''s true that mean won''t equal median for all other sets; there''s just no fixed rule for other sets.
So, if your set is created by an AP you know that mean=median; if you have another set ...”



Stuart Kovinsky
posted a reply to 3 Alligations and Mixtures Sums
in the Problem Solving forum
“I''m curious  what''s the source of these questions? I''m guessing an Indian site somewhere due to the language (and currency) used.
Be very wary of using questions that aren''t worded similarly to those on the actual GMAT  you''re not training yourself for real test questions. So, while the ...”



Stuart Kovinsky
posted a reply to DS  SETS
in the Data Sufficiency forum
“Cans is dead on  nowhere does it say that every resident belongs to at least one fitness club, so we can''t make that assumption.
It''s actually very rare for 3set questions on the GMAT to have a "none" component, which is why the formula doesn''t usually worry about that possibility; ...”



Stuart Kovinsky
posted a reply to Tough Kaplan
in the Data Sufficiency forum
“Hi,
there''s absolutely no reason why 2x couldn''t be 0; after all, 0 is even.
However, considering x=0 for statement (1) doesn''t change the answer to the question.
Remember, we need to get a "definite yes" or "definite no" for a statement to be sufficient. Let''s look ...”



Stuart Kovinsky
posted a reply to Weaken Question:
in the Critical Reasoning forum
“I got a PM asking me to post on this thread, so I will, although others have done an admirable job explaining why B is correct and why C and E aren''t.
One important factor in your CR success will be how well you understand the scope of the argument. Since the most common trap in CR is ...”



Stuart Kovinsky
posted a reply to assumption question
in the Critical Reasoning forum
“Hi,
you''re right, we don''t need the rates to be identical  that''s exactly why the language of B ("the rate.. IS SIMILAR to the rate...") is perfect for this question.
If B had said "the rate... is identical to the rate..." then it would have been overly precise and you ...”



Stuart Kovinsky
posted a reply to Simplify..
in the Problem Solving forum
“You will NEVER see that language on the GMAT  so don''t worry about it.
Pretty much the only time you''ll see "of" and need to translate into math will be with fractions or percents, e.g.
"What number is 20% of 90?"; or
"What number is 1/5 of 90?"
...”



Stuart Kovinsky
posted a reply to assumption question
in the Critical Reasoning forum
“What''s the source? If this were an inference question, then D would be correct; however, since this is an assumption question, B is definitely the right answer.
As GMATMadeEasy notes, D is just a summary of the analyst''s conclusion, whereas an assumption is a missing but necessary piece of ...”



Stuart Kovinsky
posted a reply to LSAT CR Question
in the Critical Reasoning forum
“Why oh why will no one listen to the advice given almost universally by the experts:
The LSAT is NOT a good source of practice for the GMAT.
This question, for example, is a "principle" question  one that you will almost certainly never see on the GMAT. The LSAT has many different ...”



Stuart Kovinsky
posted a reply to SC help!!
in the Sentence Correction forum
“As Arpita explains, E is the best of the lot, but even E leaves a lot to be desired (E makes it sound like sunspot cycles occur on Earth, which is nonsensical  the Earth doesn''t have sunspots!). What''s the source of the question?”



Stuart Kovinsky
posted a reply to boldface
in the Critical Reasoning forum
“Hi!
A great way to approach bolded statement question is to roadmap the stimulus just as you would a reading comp passage, treating each sentence like a miniparagraph. Just like reading comp, don''t roadmap for content  roadmap for structure. If you have a roadmap of the structure of the ...”



Stuart Kovinsky
posted a reply to OG Quant supplement 2nd edition # 42
in the Data Sufficiency forum
“Let''s examine statement (2) conceptually rather than with equations.
(2) tells us that Y is 10 more than X. From the original, we know that Y is greater than 110% of X.
Since Y is greater than 110% of X, we know that Y is more than 10% more than X.
Putting that information together, we ...”



Stuart Kovinsky
posted a reply to Anybody  Shortest/fastest way to solve this one?
in the Problem Solving forum
“Hi,
we can solve this either via algebra or picking numbers. Let''s try picking numbers.
All we know is that y>6, so let''s pick y=7. We now know that the mean is 7+3=10.
So:
Avg = (sum of terms)/(# of terms)
10 = (x + 7 + x+7 + x28 + 7x + 14)/6
60 = 10x + 28  28
60 = 10x
6 = ...”



Stuart Kovinsky
posted a reply to Work
in the Problem Solving forum
“Hi,
there''s a very simple formula to solve 2worker problems:
Combined Time = (t1*t2)/(t1+t2)
So, we simply have:
CT = (2*3)/(2+3) = 6/5
That formula is derived from the more standard work formula:
1/(combined time) = 1/t1 + 1/t2+ 1/t3 + ...
in which t1, t2, t3 and so on are ...”






Stuart Kovinsky
posted a reply to Is Right angle triangle?
in the Data Sufficiency forum
“I just wanted to address this solution, since it makes a common mistake for which test takers need to be watchful. Remember, when solving an isosceles triangle you can''t assume which angles are equal and which one is different.
Another perfectly acceptable solution to the problem is:
x + 2z ...”






Stuart Kovinsky
posted a reply to A critical Doubt
in the Data Sufficiency forum
“Just the fact that they make that statement is an indication of how poorly they understand the GMAT. What that really says is "STAY AWAY FROM OUR MATERIAL!!"”






Stuart Kovinsky
posted a reply to tenses :)
in the Sentence Correction forum
“Hi,
this seems like a poorly worded question, since as you point out "persisting" isn''t parallel to "comprise".
However, (2) is definitely wrong, since particles "persist", not "persists" (particles are plural, so we need the plural version of the ...”



Stuart Kovinsky
posted a reply to integer problem
in the Data Sufficiency forum
“Hi,
1.5 + 5 = 6.5, not 2. Since 6.5 isn''t an integer, x=1.5 is not permitted for statement one.
Here''s a good rule to remember regarding integers:
whenever you add, multiply or subtract two integers, the result will always be an integer.
Looking at (1):
x + 5 = int
x = int  5
...”



Stuart Kovinsky
posted a reply to Is Right angle triangle?
in the Data Sufficiency forum
“Let''s answer the question using minimal math, relying on our general knowledge of triangle rules.
Rephrasing the question: is one of the angles of triangle ABC 90 degrees?
1) two of the angles are equal. Neither of those angles could be 90 (since we only have a total of 180 degrees), but we ...”



Stuart Kovinsky
posted a reply to A critical Doubt
in the Data Sufficiency forum
“Hi,
if each statement seems sufficient but gives a different answer, there are two possibilities:
1) you have made a mistake (i.e. they''re not both sufficient); and
2) it''s not a proper GMAT question.
On the actual GMAT, the two statements will NEVER contradict one another. When (D) ...”



Stuart Kovinsky
posted a reply to Exponents
in the Problem Solving forum
“Hi,
that''s 100% correct. Since we can pick values that satisfy both the original inequality (which we know is true) and choice (E), we''ve proven that choice (E) COULD be true. Since it COULD be true, it''s the wrong answer to a CANNOT be true question.”



Stuart Kovinsky
posted a reply to Sequence
in the Problem Solving forum
“Hi! This question is, undoubtedly, the most often posted question on this site. If you do a search on h(100) you''ll find many many explanations.
Here''s one on which I contributed:
[url]http://www.beatthegmat.com/gmatprepnumberpropertiest8649.html?highlight=100[/url]
and there are ...”



Stuart Kovinsky
posted a reply to OG PS 98
in the Problem Solving forum
“Hi,
here''s a previous thread that discusses the question, including some geeky trivia provided by yours truly!
[url]http://www.beatthegmat.com/formulasonascalethatmeasurestheintensityofacertait9917.html[/url]”



Stuart Kovinsky
posted a reply to Exponents
in the Problem Solving forum
“Hi!
We know that y^4 must be nonnegative. So, from the original inequality we know that x^3 must be positive. Accordingly, we can conclude that x is positive.
With that in mind, since we want an answer that CANNOT be true, let''s look for a choice that requires x to be nonpositive.
A) ...”



Stuart Kovinsky
posted a reply to Voting Districts
in the Problem Solving forum
“Hi!
Here''s a thread in which I solved this question via backsolving:
[url]http://www.beatthegmat.com/gprept13262.html[/url]
Here''s another thread that has a nice algebraic solution:
[url]http://www.beatthegmat.com/problemfromthembacompracticetest1t13457.html[/url]
Enjoy!”



Stuart Kovinsky
posted a reply to Distance
in the Data Sufficiency forum
“Hi!
This question has been addressed before and the answer is E, not A. Here''s one thread that explains why:
[url]http://www.beatthegmat.com/numberlinexyandzt23333.html[/url]”



Stuart Kovinsky
posted a reply to Speed&Distance
in the Data Sufficiency forum
“Hi!
This question is a perfect place for our data sufficiency hero, "number of equations vs number of unknowns Man", to make an appearance.
Starting by analyzing the stem:
we know that distance = rate * time. We have the distance and we want to solve for the time. Accordingly, ...”



Stuart Kovinsky
posted a reply to Sum of Integers
in the Problem Solving forum
“Hi!
This question has been posted quite a few times. Here''s one discussion:
[url]http://www.beatthegmat.com/gmatnumberst10420.html[/url]
The "Search Beat the GMAT" function (top right of the page) is very useful and it''s always worth putting in a few keywords from your ...”



Stuart Kovinsky
posted a reply to Probability
in the Problem Solving forum
“Hi again Akansha!
Before we start, I want to point out a problem with this particular question. Nowhere does it say that a question has an equal chance of being true or false. Accordingly, it''s impossible to answer (and could never appear on the GMAT without that information). We''ll go ahead ...”



Stuart Kovinsky
posted a reply to Average Length
in the Problem Solving forum
“Hi Akansha!
Let''s start by analyzing the question stem. We know that:
5 pieces
Average length 124cm, so sum = #*avg = 5*124cm = 620cm
Median length 140cm; odd number of terms, so the middle term must be 140.
Our goal: to find the LONGEST POSSIBLE length of the SHORTEST piece of wood.
...”



Stuart Kovinsky
posted a reply to Actual GMAT Quant tougher than Kaplan??
in the Ask a Kaplan representative forum
“Hi Kailash,
glad to hear that things went well; that, of course, is the most important thing.
Standard deviation is definitely testable by the GMAT (as are other measurements of sets, such as median, mode and range); what I''ve never heard of, however, is a question that actually required you ...”



Stuart Kovinsky
posted a reply to Actual GMAT Quant tougher than Kaplan??
in the Ask a Kaplan representative forum
“Hi Calvin!
Did you actually see a question on the GMAT that required you to use the standard deviation formula? I''ve never heard of that happening before, so I''d be very surprised if that were the case! As Eli said, we do cover standard deviation (and those other topics that you mentioned) in ...”



Stuart Kovinsky
posted a reply to Need Expert advice
in the Reading Comprehension forum
“Hi!
The majority of applicants to Bschool don''t have a science background  and GMAC knows that. So, why does it include so many natural science passages on the exam? To test whether you can handle new information.
If you''re thrown off by the style of writing and general vocabulary ...”



Stuart Kovinsky
posted a reply to Grainco
in the Critical Reasoning forum
“Hi!
In explain questions, the stimulus is usually a set of surprising facts  there seems to be a discrepancy, contradiction or anomalous behaviour. Our job is to find the answer that, if true, resolves the issue.
We start by summarizing the situation:
Grainco''s biggest selling product ...”



Stuart Kovinsky
posted a reply to Lsat RCs Vs OG Rcs
in the Reading Comprehension forum
“Hi!
I''m not sure that I understand the fascination with using LSAT questions to practice for the GMAT. Yes, there are some similarities between the two exams, but there are also a lot of differences.
Many people like to use LSAT questions for practice because they''re perceived as more ...”



Stuart Kovinsky
posted a reply to Integer
in the Data Sufficiency forum
“Hi!
Let''s start by analyzing the question stem. If sqrt(n) is a positive integer, then n is a perfect square, e.g. 1, 4, 9, 16, ... We want to know the exact value of n.
(1) we know that sqrt(n) is an integer between 1 and 5. So, sqrt(n) could be 2, 3 or 4. Each of those gives us a ...”



Stuart Kovinsky
posted a reply to Integer
in the Problem Solving forum
“Picking numbers and elimination is a great way to tackle roman numeral questions  amar covered that approach very well. On test day, that would likely be the best approach.
Let''s take a step back, however, and go into "review mode", something you should do for every question you ...”






Stuart Kovinsky
posted a reply to GMAT Prep SC  Dr Ruth R Faden
in the Sentence Correction forum
“Hi,
GMAT grammar/style isn''t always different from standard grammar/style (in fact, it''s supposed to be the same). By the standards of North American idioms, "for doing" will pretty much never be correct (I''m pretty sure you can come up with a counterexample to any rule of English ...”



Stuart Kovinsky
posted a reply to GMAT Prep SC  Dr Ruth R Faden
in the Sentence Correction forum
“Hi all!
E is definitely the best choice. While "it" is technically ambiguous (both the White House and the Federal Advisory Committee of experts are possible antecedents), none of the other choices provide a better alternative. Remember, while the GMAT prefers nonambiguous ...”



Stuart Kovinsky
posted a reply to prep test question
in the Sentence Correction forum
“Hi!
We can quickly eliminate D and E  "both" should be modifying "reflect", so putting reflects after both messes up the sentence.
C is also out  "the extent of poor currency exchange rates keeping" is far too awkward.
A is also poorly structured. Since ...”



Stuart Kovinsky
posted a reply to Probability Question
in the Problem Solving forum
“Sure! Let''s use a very common GMAT probability question type: coin flips.
Whenever you see "at least" or "at most" in a question, you''re dealing with multiple scenarios. Here, for example, we want "at least 1 head" out of 5 flips, so acceptable results are:
...”



Stuart Kovinsky
posted a reply to DS: Packing Boxes
in the Data Sufficiency forum
“Sure!
When we say that two items are in a constant ratio, we mean that one is a multiplier of the other. For example, if:
x/y = 2/3
we can also express the relationship as:
3x = 2y
by cross multiplying by the denominators.
However, if we don''t have a simple "x/y" on the ...”



Stuart Kovinsky
posted a reply to Probability Question
in the Problem Solving forum
“Great question!
The "oneminus" method is most useful on multiple scenario questions in which there are more scenarios that we want than we don''t want.
The question will often have "at least" or "at most" in it, indicating that there are multiple possibilities ...”



Stuart Kovinsky
posted a reply to GMAT Prep
in the Data Sufficiency forum
“Hi,
there''s an infinite number of lines with that slope. For example:
y = (1/10)x + 1
y = (1/10)x + 2
y = (1/10)x + 3
and so on....
Each of those lines is parallel, but crosses the yaxis in a different spot.”



Stuart Kovinsky
posted a reply to DS: Packing Boxes
in the Data Sufficiency forum
“Hi,
(P+10)/P is a ratio, but it''s not a constant ratio; in other words, the value of the ratio changes dependent on the value of P.
You''re dead on for (2)!”






Stuart Kovinsky
posted a reply to DS Question
in the Data Sufficiency forum
“Good catch!
Remember, math wording is very precise  moving one important word around can completely change the meaning of the question.
If the question had read:
then we''d have:
y = 2.1x
The only way we can get y > 2.1x is if the question had read:
or”



Stuart Kovinsky
posted a reply to Probability
in the Problem Solving forum
“Hi! This is a truly bizarre question  what''s the source?
In any case, it can be solved fairly quickly if you can actually decipher it and understand a few underlying concepts.
First, we note that 6^k will be even for all positive values of k. Since 678463 is odd, if k is positive then ...”



Stuart Kovinsky
posted a reply to Speed Problem
in the Problem Solving forum
“Hi,
please always post both the source of your question and the answer choices. This question is tailormade for picking numbers, but because you haven''t included the choices we can''t demonstrate that approach for you.”



Stuart Kovinsky
posted a reply to Function
in the Problem Solving forum
“What''s the source of this question? An old GMAT paper test? Or is it not even from the GMAT? For those of you reading this question and incredibly confused, I wouldn''t sweat it  it''s unlikely you''ll see anything similar on test day.
You certainly aren''t expected to know any trig for the ...”



Stuart Kovinsky
posted a reply to Quick way to calculate square root of large number?
in the GMAT Math forum
“Before this gets way out of hand, something important to note: the GMAT never requires you to do crazy calculations to solve questions. GMAC knows that, in real life, people have calculators (or computers, or accounting departments) to do hard math and you''re not being tested on whether you''re a ...”



Stuart Kovinsky
posted a reply to Bob Wilber
in the Sentence Correction forum
“Hi,
based on the original sentence, it is still happening  that''s exactly why we use has.
Unless there''s an egregious error in the original, we should take the original to be an accurate picture of the author''s intended meaning. Since the author says "has ever come", the author ...”



Stuart Kovinsky
posted a reply to probability
in the Problem Solving forum
“Hi,
the problem is that you''re making assumptions based on information that you don''t have  a practice that will get you in a lot of trouble during the GMAT.
Here are some things we don''t know:
are all 100 tickets for the same lottery, or is each one for a separate lottery;
is there ...”






Stuart Kovinsky
posted a reply to road
in the Sentence Correction forum
“Hi,
D is definitely not the correct choice.
"not as hard as" needs to be followed by a noun, not an action; the usage of that phrase in D is incorrect.
For example, we could say:
Bob''s head is not as hard as Fred''s;
but we can''t say:
Bob''s head is not as hard as to ...”



Stuart Kovinsky
posted a reply to probability
in the Problem Solving forum
“Hi,
since each ticket has a 50% chance of winning, we must treat each as an independent event; nowhere does the question suggest otherwise.
Since there''s a 50% chance of winning (and, accordingly, a 50% chance of losing), we can treat this just as we would the following coin flip problem:
...”



Stuart Kovinsky
posted a reply to Aristotle SC
in the Sentence Correction forum
“When you compare costs, you use less. For example:
The sweater costs less than the pants.
When you compare the prices of two items, you use lower. For example:
The price of the sweater is lower than the price of the pants.
Remember, when it comes to idioms, the rules don''t have to ...”



Stuart Kovinsky
posted a reply to Aristotle SC
in the Sentence Correction forum
“I got a PM asking me to reply to this question, so I''ll add my input.
Here it is: the other posters have it dead on!
Even though price may seem to be noncountable, idiomatically we use "lower" and "higher" with price. Further, since we use "you" in the first ...”






Stuart Kovinsky
posted a reply to 24/sqr3
in the Problem Solving forum
“Great explanation!
To go one step further, what Maaj did is called "rationalizing the denominator"; it''s considered bad form in math to leave an irrational number (e.g. a root) in the bottom of a fraction.
Accordingly, on the GMAT you''ll almost never see a root in the denominator ...”



Stuart Kovinsky
posted a reply to prep 1
in the Problem Solving forum
“Hi!
Since each can of frozen orange juice gets mixed with 3 cans of water, we know that 1 can of concentrated OJ makes:
12oz + 3*12oz = 12oz + 36oz = 48oz of orange juice.
We want a total of 200*6oz = 1200oz of orange juice.
So, to find the number of cans we need, we simply divide the ...”



Stuart Kovinsky
posted a reply to MGMAT PS
in the Problem Solving forum
“I''ll let someone else do the math on this one  I just want to discuss it from the viewpoint of strategic elimination.
The question is:
If we understand the question, we can actually eliminate 3 of the 5 choices without even looking at the math.
First, let''s compare (A) and (B).
...”



Stuart Kovinsky
posted a reply to MGMAT PS
in the Problem Solving forum
“For the algebraphiles in the audience:
A = 2*(B/100)*C
A = 2BC/100 (which is trap answer (A)).
Our actual question:
what is A% of C?
What is 2BC/100 % of C?
2BC/100 % of C = (2BC/100)/100 * C
= 2BC/10000 * C
= BC/5000 * C
= B(C^2)/5000”



Stuart Kovinsky
posted a reply to MGMAT PS
in the Problem Solving forum
“Took me 4 reads to figure out what the question actually meant! Curse question writers who use "a" as a variable in word problems. Rewriting the question using caps (and adding a space so that "band" reads "b and"  that one really confused me too!):
We see ...”



Stuart Kovinsky
posted a reply to New items developed
in the Sentence Correction forum
“I think they''re all bad  what''s the source? If it''s 1000 SC, then let me stop you right there  don''t do those questions, they''re riddled with errors and inconsistencies.
If I were constructing the sentence, I''d say:
Until someone confirms that this is an actual GMAT question, I ...”



Stuart Kovinsky
posted a reply to GMAT Prep SC  although impoved efficiency
in the Sentence Correction forum
“What''s the source? I''d have definitely gone with A over B.
The first thing I noted about B was the use of the passive voice: "demand will be stimulated" is passive, while "it will stimulate demand" is active. It''s very rare for the GMAT to choose a passive construction ...”



Stuart Kovinsky
posted a reply to CR: Resolve Paradox
in the Critical Reasoning forum
“Hi,
I''m not sure who "800 Test Prep" is, but this is a poorly constructed question.
As noted by a couple of other posters, E explains only part of the issue  and only explains that part partially. E may explain why those stations aren''t going under, but just because they get ...”









Stuart Kovinsky
posted a reply to GMAT Prep SC  new genetic evidence
in the Sentence Correction forum
“Hi,
we can quickly narrow it down to D and E on the basis of parallelism. We have "to revamp..., [to] institute..." as the first two items in our list, so we need "[to] create" as the third item. (The "[to]" is implied throughout the list.)
We use the infinitive ...”



Stuart Kovinsky
posted a reply to Parallel SC
in the Sentence Correction forum
“The GMAT is the environmental protector of the verbal world  when in doubt, reduce reduce reduce.
If an idea is clearly expressed in two answer choices and one of those choices uses fewer words, then the shorter choice will be correct. The extra "and" that you propose serves no ...”









Stuart Kovinsky
posted a reply to princeton DS
in the Data Sufficiency forum
“Hi,
by far, the most powerful rule to remember in DS is the "number of equations/number of unknowns rule".
Here''s the basic rule:
If you have the same number of distinct, linear, equations as you have unknowns, you can answer any question about the system.
Understanding this ...”



Stuart Kovinsky
posted a reply to Remainder and 1
in the Problem Solving forum
“Hi,
first thing to note is that if you''ve reproduced the question correctly, that statement is actually sufficient to answer the question.
Q: is (k+5)/5 an integer?
As with many DS questions, we can make our lives easier by simplifying the question. Let''s break up the fraction:
Is k/5 ...”






Stuart Kovinsky
posted a reply to price
in the Problem Solving forum
“Hi!
This question is waaaay too ambiguous for the actual GMAT (what do consumption/expenditure actually mean?), but we understand the general thrust, which is a concept that the GMAT definitely tests. In the future, please make sure you include the answer choices and the source of every question ...”



Stuart Kovinsky
posted a reply to Weighted Average Problem
in the Problem Solving forum
“As an aside, let''s look at another way to solve the second question (and similar ones):
When you have two individual group averages and an overall average, you can find the weights of the group using a simple formula, illustrated by plotting the information on a number line:
...”



Stuart Kovinsky
posted a reply to Weighted Average Problem
in the Problem Solving forum
“As illustrated by the problems you posted, it depends on what information you''re given and for what information you''re solving.
First, you don''t have to assume that there are exactly 200 and 100; you can use any numbers that follow the rule given: Jar A contains twice as many red ...”



Stuart Kovinsky
posted a reply to integers> nice question
in the Problem Solving forum
“Hi,
if R is a set of all integers between two specific integers, inclusive, then by definition R will be a set of consecutive integers.
For example, if a=2 and c=10, then R = {2, 3, 4, 5, 6, 7, 8, 9, 10}.”



Stuart Kovinsky
posted a reply to If m is an integer
in the Data Sufficiency forum
“Hi,
we''re not told that m is not divisible by 2; we''re told that m/2 is not an EVEN integer.
So, for example, if m=6, then m/2 = 6/2 = 3, which is not an even integer. Is 6 odd? NO.
However, if m=5, then m/2 = 5/2 = 2.5, which is not an even integer. Is 5 odd? YES.
Since both even ...”



Stuart Kovinsky
posted a reply to GMATPrep Problem
in the Problem Solving forum
“As a followup to Mitch''s post (backsolving is a great way to solve this question), we can use common sense and a bit of arithmetic to quickly eliminate two of the five choices, making backsolving even more viable.
We know that the correct answer is the product of x and (x1). Since this is the ...”



Stuart Kovinsky
posted a reply to integers> nice question
in the Problem Solving forum
“Hi!
4, 5, 7 and 10 are not consecutive numbers, so the rule doesn''t apply.
"Consecutive" means that the numbers are a fixed distance apart. Some examples of sets of consecutive numbers to which the rule applies:
{1, 2, 3, 4}
{3, 6, 9, 12}
{10, 5, 0, 5, 10}
{11, 14, 17, 20}
...”












Stuart Kovinsky
posted a reply to Type of CR question  PR CAT
in the Critical Reasoning forum
“Hi!
The question asks us to determine the accuracy of the study. Accordingly, the correct answer must be a fact that''s directly related to the study itself, not the results.
This distinction is very important; we''re not being asked to strengthen or weaken the study''s conclusion  we''re ...”






Stuart Kovinsky
posted a reply to Absolutely Value Inequality
in the Problem Solving forum
“Hi!
I''ve bolded the key words in the question to emphasize what we''re really being asked.
While you''re correct that the inequality in (B) includes all of the points in the shaded part of the number line, it''s also true that (B) includes some points that aren''t in the shaded region, e.g. ...”



Stuart Kovinsky
posted a reply to What is the value of Y
in the Data Sufficiency forum
“Just a quick point on solving absolute values, although it didn''t turn out to make a difference to this particular question.
Remember, the absolute value of anything is nonnegative; "nonnegative" is NOT the same thing as positive.
So, if we solve a bit more precisely:
3*abs ...”



Stuart Kovinsky
posted a reply to tricky odds and evens problem
in the Data Sufficiency forum
“Hi!
I really doubt that I''d even attempt to tackle a question like this algebraically, since the math is a bit on the nutty side. The tougher the questions get, the more you need to use alternative approaches if you want to beat the clock.
In all likelihood, I''d pick numbers until I saw a ...”



Stuart Kovinsky
posted a reply to Several years ago the diet industry
in the Sentence Correction forum
“Here''s the important thing to remember about pronoun ambiguity: it''s a style issue, not a grammar issue. So, if you have to choose between two choices, both of which are grammatically correct but one of which is ambiguous, go with the nonambiguous choice.
However, when all the choices ...”



Stuart Kovinsky
posted a reply to OG 12 Q 33
in the Critical Reasoning forum
“Hi,
anytime a question asks you to draw a conclusion based on the statements in the stimulus, it''s an inference question. Since this question asks us what "must be true on the basis of the statements... above", it falls clearly into that category.”






Stuart Kovinsky
posted a reply to Word problem (book answer looks dubious)
in the Data Sufficiency forum
“Hi,
we can quickly determine that (2) is insufficient alone, since we''re not told that he sold the bracelet for the original asking price; we certainly can''t assume such to be the case. For all we know he had to discount the bracelet 12 times before he eventually sold it.
Since we don''t ...”



Stuart Kovinsky
posted a reply to tricky odds and evens problem
in the Data Sufficiency forum
“Hi,
you''re 100% correct that on the GMAT the two statements will never conflict; however, there''s no conflict on this particular question.
(1) tells us that z is 2/3 of an even integer; (2) tells us that z is 2/5 of an even integer; however, nowhere does it say that z is 2/3 and 2/5 of the ...”



Stuart Kovinsky
posted a reply to GMAT TestPrep Question
in the Data Sufficiency forum
“Hi!
manpsingh''s approach is good, and perhaps easier to understand if we look at the information slightly differently.
First, let''s think about the question stem (always a good first step in DS).
We see that we have a perfect square on top and a perfect square on the bottom; however, ...”



Stuart Kovinsky
posted a reply to Divisibility problems
in the Data Sufficiency forum
“Hi!
You can certainly solve this type of problem by applying divisibility rules, but like almost all data sufficiency yesno number property problems, picking numbers is also an excellent approach.
When you pick numbers in data sufficiency, it''s vital to follow 2 steps:
1) pick a number ...”



Stuart Kovinsky
posted a reply to Number Properties
in the Problem Solving forum
“Hi!
The question is correct.
Both of you assumed that x has to be an integer, something not stipulated by the question.
Since x doesn''t have to be an integer, one cannot assume that if 9 is a factor of 2x, 9 must also be a factor of x.
For example, if you plug in x=4.5, you get:
9 is ...”



Stuart Kovinsky
posted a reply to # of 5 digit numbers
in the Problem Solving forum
“Hi!
The search bar is a very valuable tool on Beat the GMAT, since many of the same questions get posted in different threads.
For example, I did a search on "how many fivedigit numbers" and got 4 pages of responses.
Here are some links to other threads discussing this question:
...”



Stuart Kovinsky
posted a reply to GMAT STATISTICS
in the Problem Solving forum
“Hi,
when looking at statistical data, it is, not surprisingly, all about the numbers.
Consequently, regardless of whether you''re talking about people or animals or money, you still just view each data point as a number in a set.
Accordingly, there''s really no such thing as the ...”



Stuart Kovinsky
posted a reply to sequence
in the Problem Solving forum
“Hi,
since the first term is 1, and since we double to find the next term, we can quickly see that the nth term of the sequence is simply 2^(n1). In other words:
term1 = 2^0
term2 = 2^1
term3 = 2^2
and so on.
So, the 16th, 17th and 18th terms will be:
2^15, 2^16 and 2^17.
Next, ...”



Stuart Kovinsky
posted a reply to Aristotle SC
in the Sentence Correction forum
“Hi,
(D) commits the unforgivable error of changing the meaning of the sentence; since the original is written in the present tense, we shouldn''t change to the past unless that was clearly the author''s intention.
The problem with (A) is lack of parallelism; "is roasting... while he ...”



Stuart Kovinsky
posted a reply to 1000 DS section 17 question 20
in the Data Sufficiency forum
“Hi Prashant,
are you sure that you''ve posted (1) correctly? In its current form, (1) is definitely sufficient.
Algebraically:
5^(k1)> 3000
multiplying both sides by 5:
5^(k1) * 5^1 > 15000
5^(k1+1) > 15000
5^k > 15000
and if 5^k is more than 15000, it''s ...”



Stuart Kovinsky
posted a reply to Probability questPrinceton Review
in the Problem Solving forum
“For combinations vs permutations, the important question to ask is "does order matter".
If order doesn''t matter, use combinations; if order does matter, use permutations.
Here''s another way you can think about it: After I''m done selecting the subgroup, am I going to do anything ...”



Stuart Kovinsky
posted a reply to least value venn diagram
in the Problem Solving forum
“Hi Nitin,
here''s a good general rule for GMAT mini/maxi questions: whenever you''re asked to minimize or maximize one part of a problem, do so by maximizing or minimizing other parts of the problem.
Here''s a simpler example:
We think: we want to maximize the number of cars with AC, so ...”



Stuart Kovinsky
posted a reply to One more intrestg one  its a common 1 but nice 1
in the Sentence Correction forum
“whats the difference when we say sloth sleep 15 hours a day and when we say the sloth sleeps 15 hours a day . Are both sentences acceptable when we are talking about the sloth/sloths in general ?[/quote]
Both are acceptable, as long as they agree with and make sense in the context of the other ...”



Stuart Kovinsky
posted a reply to Aristotle RC <700 level>
in the Sentence Correction forum
“I''m really not in love with any of the choices (what''s the source? I''ve never heard of Aristotle  well, at least the Aristotle I have heard of lived a couple of millenia preGMAT), but B is the clear winner of the available options.
Let''s look at C again:
(C) compares 2009 to the ...”



Stuart Kovinsky
posted a reply to Brutal SC #54
in the Sentence Correction forum
“Hi! Old question, but still worth a look.
"it" doesn''t refer to anything sensical in this sentence. Let''s construct a similar, but simpler, example to illustrate.
vs
Does "they" make sense in this statement? No, because we''re comparing two facts about the ...”






Stuart Kovinsky
posted a reply to Probability questPrinceton Review
in the Problem Solving forum
“Hi Ankit,
the 9 items are different, it''s just that some of them are the same colour; there are 9 physical jars from amongst which to choose, so 9 is the total number of objects.
The only time (at least on the GMAT) that we worry about objects being distinct is for permutations  i.e. we''re ...”



Stuart Kovinsky
posted a reply to Probability and combinations
in the Problem Solving forum
“Hi,
on most complicated probability problems on the GMAT, the "one minus" approach is the quickest way to solve.
This approach is based on the equation:
Prob(what you want) + Prob(what you don''t want) = 1
which rearranges to:
Prob(what you want) = 1  Prob(what you don''t ...”



Stuart Kovinsky
posted a reply to Mixture with Alligation
in the Problem Solving forum
“Hi!
I''ve never heard of the "alligation" method  does it involve feeding part of the mixture to alligators? Sounds dangerous!
As an aside, this question is seriously flawed and impossible to answer in its current form, since you can''t answer a "how much" question unless ...”



Stuart Kovinsky
posted a reply to any simpler way..
in the Problem Solving forum
“While this question would never appear on the GMAT ("at least twice greater than" makes no sense  clearly the author meant to say "at least twice as much as"), it illustrates an interesting strategic approach.
Let''s start with a fundamental rule of the exam: there can only ...”



Stuart Kovinsky
posted a reply to Set of 3
in the Problem Solving forum
“You know that it''s going to be a horribly worded question as soon as you see the word "curriculums" in the first sentence (and "participate in some curriculums" is also nonidiomatic, even if "curriculums" was a word).
If you find nonofficial questions written in ...”






Stuart Kovinsky
posted a reply to Aristotle Q53
in the Sentence Correction forum
“Hi,
I highly doubt that you''d ever see these two choices on the GMAT  there''s a small stylistic difference, but both are essentially equal in terms of "goodness".
I would consider whether "is" is the grammatically correct verb for the last part of the sentence; since ...”



Stuart Kovinsky
posted a reply to Artificial reefs
in the Critical Reasoning forum
“Hi!
Any chance you can repost the question with the original language? The current version has so many grammatical errors that it actually hurts my head to read it!
Leaving out articles (e.g. "a", "the", "an"...) and using improper tenses (e.g. "sea life ...”






Stuart Kovinsky
posted a reply to permutations and combinations
in the GMAT Math forum
“Hi!
First, we need to know a trick for mutliples of 3: the sum of the digits of any multiple of 3 will also be a multiple of 3.
So, for example, 54321 is a multiple of 3, since 5+4+3+2+1=15 and 15 is a multiple of 3.
Now we need to see which combinations of those 5 digits will sum to a ...”



Stuart Kovinsky
posted a reply to average
in the Data Sufficiency forum
“Hi!
We see we''re being tested on averages, so let''s start by jotting down the average formula:
average = (sum of terms)/(# of terms)
We know that the average is x and that the income of one person increases by 25%. We don''t know the number of people in the group or the sum of their ...”



Stuart Kovinsky
posted a reply to ps:pnc
in the Problem Solving forum
“Not a real GMAT question (on the GMAT, "palindrome" would be defined, there would be more specificity regarding repeating numbers and, of course, there would be answer choices), but an interesting counting question nonetheless.
Ignoring the actual numbers, let''s use X, Y and Z to ...”









Stuart Kovinsky
posted a reply to Clarification for Square Roots
in the Problem Solving forum
“Hi,
you answered your own question early on, when you said:
By mathematical convention, the "√x" should be read as "the nonnegative root of x" (so √0 = 0, but in all other cases √x is the positive root of x). Like all math rules, this applies regardless of how ...”



Stuart Kovinsky
posted a reply to We who
in the Sentence Correction forum
“Hi!
"then" doesn''t change the meaning of the sentence, it''s just grammatically incorrect. "We who then graduated ... in the 1960s..." implies that an action took play before the "then", but there''s no such action in the sentence.
For example, if a sentence ...”



Stuart Kovinsky
posted a reply to Stuart Kovinsky  did i get your solution wrong??
in the Data Sufficiency forum
“Hi,
as Ian notes, if you have a question about a post in an existing thread, it''s much more efficient to just reply to that thread rather than start a new one.
In any case, Ian answers your specific question in the thread he linked (thread hijacker!) and I believe his answer is the same as on ...”



Stuart Kovinsky
posted a reply to 6 married couples
in the Problem Solving forum
“Hi!
Whenever you make multiple simultaneous selections, you can treat the question as though you''re selecting the items one at a time; let''s do that on this question.
Our first person can be anyone, so there''s a 12/12 chance that the person is "safe".
Once we choose our first ...”



Stuart Kovinsky
posted a reply to Cost to edge a flower garden
in the Problem Solving forum
“Hi!
Vivian''s advice is dead on; the old adage "you get what you pay for" definitely applies to most free GMAT questions available on the web. Probably the biggest advantage of going with "brand name" materials is that you know that the top prep companies didn''t get to where ...”



Stuart Kovinsky
posted a reply to Product of consequtive integers problem
in the Problem Solving forum
“Hi!
Our number has to be a multiple of 990. The only way it could possibly be multiple of 990 is if it contains all of the prime factors of 990.
Another way to phrase the question is:
if n!/990 is an integer, what''s the smallest possible value of n?
So, 990 must divide into n!, which ...”



Stuart Kovinsky
posted a reply to Cost to edge a flower garden
in the Problem Solving forum
“Hi!
The question definitely isn''t worded clearly, since the common interpretation would be surrounding the flower bed with stones; however, by reverse engineering the choices it''s clear that''s not the case.
So, ignoring "filling in the corners" but using the rest of your ...”



Stuart Kovinsky
posted a reply to Coordinate question from BTG practice questions
in the Data Sufficiency forum
“Hi!
(1) is insufficient, because it doesn''t tell us anything else about the line. It could simply be the line y=2, in which case it wouldn''t pass through quadrant III, or it could be any line with a positive slope, in which case it would pass through the quadrant.
(2) tells us that the line ...”



Stuart Kovinsky
posted a reply to Selection Problem
in the Problem Solving forum
“Hi!
This question has been discussed many times  I ran a search on "4 people have exactly 1 sibling" and hit a ton of threads.
Here''s one in which I explain the question:
[url]http://www.beatthegmat.com/siblingprobabilityt46183.html[/url]
and there are many others if you ...”



Stuart Kovinsky
posted a reply to museum
in the Critical Reasoning forum
“Hi,
some always means "at least one"  we can''t quantify any more than that.
Since some means "at least one", when we deny (i.e. take the opposite of) some we get "not at least one", which translates as "none".
In this particular question, that ...”



Stuart Kovinsky
posted a reply to A set consists of of several different integers. Is the pr..
in the Data Sufficiency forum
“Hi!
It doesn''t matter if the list is in order. "Greatest" means the biggest number in the list and "smallest" means the smallest number in the list, regardless of how you arrange the terms. For example, in the sets:
{1, 2, 3, 4, 92}
and
{2, 4, 92, 3, 1}
the ...”



Stuart Kovinsky
posted a reply to a data from gmatclub
in the Data Sufficiency forum
“Hi!
It''s key to understand exactly what a statement is telling you.
(1) x^2  2*x + A is positive for all x
To satisfy this statement, we have to have an A that makes the expression positive for EVERY POSSIBLE value of x.
Well, if x=0, then the expression simply equals A. So, in order ...”









Stuart Kovinsky
posted a reply to museum
in the Critical Reasoning forum
“A tool you can use for assumption questions is the Denial Test.
The correct answer to an assumption question is something that must be true for the argument to hold; an essential building block of the argument.
The opposite of the correct answer will show that the argument is wrong; it will ...”






Stuart Kovinsky
posted a reply to properties of a work of art
in the Critical Reasoning forum
“Hi!
First thing to note about this question  it''s a retired question from an old LSAT exam. Further, although assumption questions do appear on the GMAT, it would be very rare for them to be this complex.
However, we can still treat this as we would a simpler assumption question: identify ...”






Stuart Kovinsky
posted a reply to ps  square in square
in the Problem Solving forum
“Mitch has provided a great example of picking numbers, so let''s try something different: applying basic principles and avoiding math.
First, we need to understand the question: we have a smaller equilateral triangle inside a larger one and the triangles are similar  in other words, the ...”



Stuart Kovinsky
posted a reply to og 82
in the Problem Solving forum
“Picking numbers is a great approach and, using a bit of common sense, you should realize that you only have to try two numbers.
First, we recognize that if n is a multiple of 3 then every choice will also be a multiple of 3.
Second, since "3" is the important number, we recognize ...”









Stuart Kovinsky
posted a reply to ds:numbers
in the Data Sufficiency forum
“A good test of our ability to avoid complex calculations!
(1) the range given only contains one multiple of 5 (1240), so (1) is certainly sufficient: eliminate (B), (C) and (E).
(2) we could divide all 3 parts by 3, but we''d really rather avoid the math. There are three ways we can deal ...”



Stuart Kovinsky
posted a reply to ps:pnc
in the Problem Solving forum
“Hi again!
When we''re selecting a subgroup out of a larger group, think combinations. As always, let''s start by jotting down the combinations formula:
nCk = n!/k!(nk)!
in which n is the total number of objects and k is the number in our subgroup.
In this question, we''re making two ...”



Stuart Kovinsky
posted a reply to ps:probability
in the Problem Solving forum
“Please post the exact wording of the original question along with the source. On this particular question we can determine what''s being asked, but grammatical errors (of which there are a few in this post) can alter the meaning of a question. Also, please post the answers, since many GMAT ...”



Stuart Kovinsky
posted a reply to although certain great apes
in the Sentence Correction forum
“"consider" is often tested on the GMAT because it''s one of the rare verbs that''s generally not followed by a preposition.
For example, a correct sentence is:
However, many people are tempted to say:
or
both of which are idiomatically incorrect.
However, as with ...”



Stuart Kovinsky
posted a reply to MGMAT CAT 6
in the Data Sufficiency forum
“Hi!
Some tricky working in (1) which we need to carefully translate, but once we do it''s clear that each statement is sufficient alone.
Q: What''s the probability that Memphis isn''t chosen to host?
First, we need to recognize that if we can answer "what''s the probability that ...”



Stuart Kovinsky
posted a reply to PS  divisor>1 Q
in the Problem Solving forum
“Hi!
I''d write out all of the perfect squares less than 75 (since that''s the biggest answer):
4, 9, 16, 25, 36, 49, 64
and then simply look for the choice for which none of those are a factor.”



Stuart Kovinsky
posted a reply to a/b > b/c  inequality
in the Problem Solving forum
“Hi,
you have to be very careful when manipulating inequalities that involve variables.
Remember, when you multiply or divide both sides by a negative, you have to swap the inequality. Since we don''t know the signs of b or c, it''s NOT safe to cross multiply.
Let''s pick numbers to ...”






Stuart Kovinsky
posted a reply to Looking Too Deep?
in the Data Sufficiency forum
“Hi!
What''s the source of this question? I ask because there''s important wording missing from the statements in order for (B) to be the correct answer.
You''re 100% right in your counterargument to (2) being sufficient. For (2) to be sufficient alone, it should read:
Both statements ...”



Stuart Kovinsky
posted a reply to Probability:)
in the Problem Solving forum
“Hi!
Check out:
[url]http://www.beatthegmat.com/trythisoneonforsizecourtesyofmanhattangmatt51512.html?cityevent=Chicago40706[/url]”



Stuart Kovinsky
posted a reply to Combinotrics:)
in the Problem Solving forum
“Hi!
To solve this, let''s start with the easier embedded question:
In how many ways can 6 people be arranged in a line?
When we''re arranging n distinct objects, there are n! possible arrangements.
So, there are 6! = 6*5*4*3*2 = 720 total arrangements.
(Another way to solve: for the ...”



Stuart Kovinsky
posted a reply to A new strategy for releasing the seals
in the Sentence Correction forum
“Hi,
what''s the specific source? If you provide the details, I''ll get the question edited.
We can definitely introduce new words into the correct answer. Here''s the rule to follow:
So, if the new word clears up ambiguity but doesn''t change the meaning of the sentence, then it ...”



Stuart Kovinsky
posted a reply to fruit seller loses
in the Problem Solving forum
“First, there are lots and lots of people who would have no idea what "loses the selling price of 4 oranges" means  especially people for whom English isn''t their first language.
So, even though I always understood what you meant, that''s not the point.
The point is that if you''re ...”



Stuart Kovinsky
posted a reply to fruit seller loses
in the Problem Solving forum
“I must have a masochistic streak in me  I really don''t know why I keep replying to these threads!
This question isn''t written in proper English. What does "loses the selling price of 4 oranges" mean? What does "loss percent" mean? That language is way too ambiguous for ...”



Stuart Kovinsky
posted a reply to units sold after the reduction
in the Problem Solving forum
“Hi,
I think there''s a mistake in the question, since the stem clearly states that there''s a 28% increase in sales (a term which usually refers to the number of units sold). Did you mean to say that there''s a 28% increase in gross revenue?
Alternatively, if that part of the question is ...”






Stuart Kovinsky
posted a reply to A new strategy for releasing the seals
in the Sentence Correction forum
“Hi!
I really hope that you copied the question incorrectly, since the nonunderlined part is incorrect; it should read "A new strategy for releasing seals..." (the definite article "the" makes no sense in this sentence). If you''ve copied it verbatim, please let me know the ...”



Stuart Kovinsky
posted a reply to Labor Department’s employment report
in the Sentence Correction forum
“This question is a great illustration of the power of scan and eliminate, the essence of the Kaplan Method for Sentence Correction.
After reading the sentence once, if nothing jumps out at you, scan the choices looking for differences.
The easiest place to spot a difference is right at the ...”



Stuart Kovinsky
posted a reply to Inuits of the Bering Sea were
in the Sentence Correction forum
“Hi!
it would be idiomatically acceptable to say "They were in isolation." It would also be acceptable to say "They were isolated from contact with X." However, it''s not acceptable to say "There were in isolation from contact with X."
Since (A) and (C) both have ...”



Stuart Kovinsky
posted a reply to although certain great apes
in the Sentence Correction forum
“Hi,
two independent clauses must be connected by one and only one connector. In (B), "Although" serves precisely that function.
So, unless you''ve mistyped one of the other responses, (B) must be the correct answer.
(A) is passive; "it" has no proper antecedent.
(C) ...”



Stuart Kovinsky
posted a reply to Does 'constant' also mean integer?
in the GMAT Math forum
“Hi,
"constant" is simply the opposite of "variable"; since the GMAT only deals with the set of real numbers, for GMAT purposes a constant is any fixed real number (an integer, fraction, positive, negative, 0, irrational number like pi, etc...).”



Stuart Kovinsky
posted a reply to Chance of Rain
in the Problem Solving forum
“For a discussion of coin flip and pseudocoin flip questions (the question on this thread is one of the latter), check out:
[url]http://www.beatthegmat.com/coinflipquestionsmadeeasyt17911.html#75414[/url]”



Stuart Kovinsky
posted a reply to standard deviation
in the Problem Solving forum
“Hi!
I have some bad news for you and some good news.
The bad news is that your calculation of SD is way off; the SD of {5, 10, 15} is NOT 5.
The good news is that you don''t actually need to know how to calculate SD for the GMAT; you merely have to have a basic idea of what SD is and when ...”



Stuart Kovinsky
posted a reply to Weird Question
in the Problem Solving forum
“Here are some discussions:
[url]http://www.beatthegmat.com/whatismnt57268.html[/url]
[url]http://www.beatthegmat.com/additiontablegmatprepquestiont11305.html[/url]
[url]http://www.beatthegmat.com/gmatprepadditiontableshownabovet22030.html[/url]
...”






Stuart Kovinsky
posted a reply to y > 0
in the Problem Solving forum
“The question could definitely be worded more clearly (I''m not sure of the source, but it sounds "homemade"). Let''s assume, for the sake of the question, that it reads "MUST BE positive EXCEPT" instead of "IS positive EXCEPT". Even with that change, (D) and (E) both ...”



Stuart Kovinsky
posted a reply to benchmarking values  fraction
in the Problem Solving forum
“Hi!
First, I wholeheartedly agree with Brent  please provide the answer choices for every question that you post, since many strategic approaches rely on the choices.
Dealing with your specific question, however:
Since we''re rounding 10/22 UP to 1/2, I''d round 5/18 DOWN to 1/4  that ...”






Stuart Kovinsky
posted a reply to OG 11 DS #132
in the Data Sufficiency forum
“Hi,
first off, it''s important to understand exactly what (2) says  I''ve seen many people get this question wrong because they misinterpret (2).
This means that if you take any two distinct factors of n, you''ll get an odd difference. How is this possible? Only in 1 case: n must have ...”



Stuart Kovinsky
posted a reply to GMATPrep Quetsion
in the Data Sufficiency forum
“Sure! Let''s start by breaking down the question stem.
We know that 72% of males and 80% of females have applied to college. We want to know that percent of the entire class is male.
We think: lots of missing information; since the question is asking us for a percent, not an actual number, ...”



Stuart Kovinsky
posted a reply to GMATPrep Quetsion
in the Data Sufficiency forum
“Hi,
in it''s current form, (2) is not sufficient.
However, if (2) were to read:
then we could use weighted averages (or ratios) to figure out what percent of the senior class is male.
Are you sure that you reproduced the question correctly? What''s the source?”



Stuart Kovinsky
posted a reply to O.G Quant Review
in the Problem Solving forum
“The only information we have about x and y is that they''re positive integers, so there will be very few conclusions we can draw about their greatest common factor.
However, here''s one thing we do know: the greatest common factor of any positive integer is the integer itself.
Accordingly, ...”









Stuart Kovinsky
posted a reply to [CR][PnR] HSPA posts
in the Data Sufficiency forum
“We see a yes/no inequality question with variables. We think: be careful about multiplying or dividing both sides by a variable  if the variable could be negative, weird things may happen!
(1) we immediately consider p=r=0. In this case, 1/p is undefined, so it''s impossible to answer the ...”



Stuart Kovinsky
posted a reply to Is xy + xz = 0
in the Data Sufficiency forum
“The question becomes much simpler if you simplify the question!
Is xy + xz = 0?
Is x(y + z) = 0?
When will this be true? If x=0 or (y + z) = 0.
(1) x = 0... sufficient!
(2) y + z = 0... sufficient!
Each statement is sufficient alone  choose (D).”



Stuart Kovinsky
posted a reply to Functions junctions mess!
in the Problem Solving forum
“Hi!
You made a couple of errors.
First, the first term is 1/g(2), not g(2). So, subbing in:
1/g(2) = 1/(6/1) = 1/6
and the second term is:
1/g(x) = 1/((x^2 + 2) / (x  1)) = (x1)/(x^2 + 2)
Taking the product of those two terms:
(1/6)*(x1)/(x^2 + 2)
= (1)(x1)/(6)(x^2 + 2)
...”



Stuart Kovinsky
posted a reply to Geometry  Circles and Squares.
in the Data Sufficiency forum
“For DS, the instructions Do say that diagrams are not drawn to scale. From the Official Guide (p24 of 12th ed.):
Based on the first point, we know that DS diagrams are not necessarily drawn to scale and we can''t rely on the way that they appear.
Based on the third point, we know that ...”



Stuart Kovinsky
posted a reply to MGMAT CAT 4
in the Data Sufficiency forum
“I''m really not sure where you came up with that pattern, but it definitely doesn''t match what will happen on this question.
If you take ANY 7 numbers ending in 3 and multiply them together, the units digit of the full product will be the same as the units digit of 3^7.
Now, powers of 3 ...”



Stuart Kovinsky
posted a reply to More Primes
in the Problem Solving forum
“As noted in my post above, you multiply the value of each chip by the values of all of the other chips.
So, if you have 1 blue chip, the total value of the blues is:
1^1 = 1.
Similarly, if you have 10 blue chips, the total value of the blues is:
1^10 = 1
not
1*10 = 10
which is ...”



Stuart Kovinsky
posted a reply to More Primes
in the Problem Solving forum
“You''re misinterpreting the statement to read "the sum of the purple chips is greater than that of the green chips, but less than that of the red chips"; it''s not the sums that are being compared, but the values of the individual chips.
As we can see from the question:
...”



Stuart Kovinsky
posted a reply to MGMAT CAT 4
in the Data Sufficiency forum
“Interesting question!
As always, one key to success is to understand exactly what the question is asking. Here, we only care about the units (i.e. ones) digit of n; accordingly, we only care about the units digit of (243^x)*(463^y).
Since both terms end in "3", we''re multiplying ...”



Stuart Kovinsky
posted a reply to MGmAT CAT 4
in the Problem Solving forum
“Hi,
we can''t prove (I) is false, but that''s not what we need to do to disqualify it  we merely need to show that it COULD be false.
We can certainly pick numbers to show that (I) need not be true, let''s just change the days that I used for my counter example to (III):
A''s regular wage ...”



Stuart Kovinsky
posted a reply to MGMAT CAT  Root of a Square
in the Problem Solving forum
“Based on the question, we know there are at least two values for x.
If there were only 1 possible value, the GMAT wouldn''t use the word "could".
We also see squares and roots, alerting us to a positive and negative solution.
Now, let''s put on our GMAT question writer hats ...”



Stuart Kovinsky
posted a reply to MGMAT CAT  ratio'S prob
in the Problem Solving forum
“We''ve seen a good algebraic solution, so let''s attack the question strategically, by backsolving.
When the answer choices are numbers and the question is simple (e.g. "how many red marbles could there be?"), then backsolving is often a very effective approach.
If you can''t quickly ...”



Stuart Kovinsky
posted a reply to MGmAT CAT 4
in the Problem Solving forum
“Let''s think things through logically:
1) we know that they worked the same number of hours during the week;
2) we know they earned the same total salary for the week;
3) we know that Alan''s regular wage is higher; and
4) we know that Barney gets paid double time on Saturdays.
If they only ...”



Stuart Kovinsky
posted a reply to Permutations
in the Problem Solving forum
“Hi!
This isn''t actually a permutations question, since order doesn''t matter. It can be solved with either combinations or probability.
Here''s another thread discussing the question: [url]http://www.beatthegmat.com/isuckatprobabilityneeddesperatehelpt8927.html[/url]”



shovan85
posted a reply to Permutations
in the Problem Solving forum
“Need to form a group of 12 people.
This can be done in C(15,12) = 455
2/3 of the 15 are Men = 10 men
1/3 of the 15 are women = 5 women
in the formed group 2/3 at least are needed to be men,
so at least 8 men needed.
C(10,8) * C(5,4) + C(10,9) * C(5,3) + C(10,10) * C(5,2)
= 225 + 100 + ...”



Stuart Kovinsky
posted a reply to Distinct members and committee
in the Problem Solving forum
“While I admire your ambition, I''m a bit confused about your motives. Are you studying for the GMAT? If so, why not work on the questions that are actually out there rather than trying to create some of your own, especially since you''re just getting started?
A big part of GMAT success is ...”



Stuart Kovinsky
posted a reply to GMAT Club PS question 2
in the Problem Solving forum
“Hi,
if t=u=0, then (C) would be true and (A) would be false, so there''s at least some difference between the options.
However, if two answer choices were exactly the same, and you noticed that fact, then you could quickly eliminate both choices (unless it''s a roman numeral question); since ...”



Stuart Kovinsky
posted a reply to Percents and increasing Speed
in the Problem Solving forum
“Hi,
it''s very useful to know the basic fractiondecimalpercent conversions by heart, namely:
1/2 = .5 = 50%
1/3 = .333 = 33.3%
1/4 = .25 = 25%
1/5 = .2 = 20%
1/6 = .1667 = 16.67%
1/8 = .125 = 12.5%
1/9 = .111 = 11.1%
1/10 = .1 = 10%
1/20 = .05 = 5%
(1/7 = approx .14 = approx 14%)
...”



Stuart Kovinsky
posted a reply to Distinct members and committee
in the Problem Solving forum
“I''m not sure why you''d modify a Kaplan question, only include 4 answer choices (instead of the 5 that appear on the actual GMAT) and leave it open to multiple correct answers, even though the question itself implies that there''s only 1 possible answer.
As a result, the way you''ve modified it ...”






Stuart Kovinsky
posted a reply to data sufficiency problem
in the Data Sufficiency forum
“Sometimes it helps to think of real world scenarios to help you visualize what''s going on in a question.
We know that the top and bottom lines are parallel, but don''t know the relationship between the vertical lines (PQ and SR).
Picture a street with houses on both sides. PS is the north ...”



Stuart Kovinsky
posted a reply to Exponents
in the Data Sufficiency forum
“As is the case with a lot of complex DS questions, we can make our lives easier by simplifying the question.
We know that p and q are both nonzero integers. So, when will p^(3q) NOT be an integer?
Well, if q is positive, then p^(3q) will always be an integer.
If q is negative, then p^(3q) ...”



Stuart Kovinsky
posted a reply to primesaturated
in the Problem Solving forum
“Hi,
you''re not expected to be familiar with that term before seeing this question  the question provides the definition.
According to the definition, "prime saturated" means that the product of the distinct prime factors must be less than the root. Once we understand the ...”



Stuart Kovinsky
posted a reply to GMAT PREP QUESTION
in the Problem Solving forum
“This question is typical of the most common way the GMAT is currently testing standard deviation. All you need to solve is a very basic understanding of what SD is  the question itself is much simpler than it seems.
To solve quickly every time, draw a number line and put the mean in the ...”



Stuart Kovinsky
posted a reply to Probability Question
in the Problem Solving forum
“Hi,
when you select multiple items simultaneously, you can treat the question as though you select them one at a time, without replacement.
So, our question becomes:
If there are 2 red marbles and 3 green marbles in a bag, and you select a marble, then select a second marble without ...”



Stuart Kovinsky
posted a reply to long equation !! stuck
in the GMAT Math forum
“First up, what''s the question? Solve for a possible value of n? Solve for all the values of n? Without the question (and choices), it''s impossible to find the best possible approach.
Assuming that we need all the values of n, I''d start with Brett''s analysis:
n is common to all 3 terms, ...”






Stuart Kovinsky
posted a reply to Factor Problem
in the Data Sufficiency forum
“Hi Yvonne,
Let''s start by simplifying the question:
When will xy be divisible by 9? When xy contains all the primes contained by 9. So, rephrasing the question:
On to the statements!
(1) xy is divisible by 6, or:
xy contains at least one "2" and and least one ...”



Stuart Kovinsky
posted a reply to GMAT Club DS question
in the Data Sufficiency forum
“Hi,
Mitch''s explanation is spot on (as usual), I just want to focus on the specific mistake you made, since it''s probably the most common way that test takers go wrong in data sufficiency.
When you evaluate a statement, you must take its truth for granted. In other words, the only numbers ...”






shovan85
posted a reply to Investment funds and pharmaceutical corporations
in the Critical Reasoning forum
“(A) Product development is too costly for a single corporation to fund without research and development partnerships.
(B) Product development partnerships between pharmaceutical corporations and investment funds are more common now than they were in the recent past.
(C) Product development ...”







