[720 Q49 V40] My Blog: Errors and lessons learned

Guest · Guest

mayonnai5e - the link to your blog doesn't seem to be working for me..... is it still up and running or have you taken it down? thanks

mayonnai5e · Posted: Fri Sep 21, 2007 7:02 am Post subject:

I had an old blog that I was running on blogspot, but I took it down to track all my progress on this site instead.

mayonnai5e · Posted: Fri Sep 21, 2007 4:34 pm Post subject:

Investigation of N = Dq + r:

So one day while I was sitting at a cafe in Paris, I decided to study this equation. This equation can be used to describe any number. On the GMAT, you'll likely see this equation in the format:

Y = Xq + r, where 0 <= r < X

But I'll represent it with different variables to make it more clear what the variables represent:

N = Dq + r

where
N = any Number
D = any Divisor
q = quotient of N/D
r = remainder of N/D

The most basic form of this equation you'll see is:

N = 2q ----------> EVEN
N = 2q + 1 -----> ODD

Why are these true? N = 2q is the same as N = 2q + 0 where 0 is the remainer when N is divided by 2. So N is divisible by 2 and N must be even. For the other, the remainder is 1 when N is divided by two so it must be odd.

# 147 OG11: If n is a positive integer, is n^3 - n divisible by 4?
(1) n = 2k + 1, where k is an integer

You can see that n is odd from stmt 1.

Now, here's the most complex stuff...

This equation can also be represented as N = q (r/D). This is not supposed to be multiplication; think 7.5 as 7 and one half.

For example, N = 8, D = 3:
8 = 2 (2/3)

N = 8, D = 5:
8 = 1 (3/5)

* Note the (r/D) portion implies that r is not divisible by D. If r were divisible by D, then there would be no remainder. In addition, the (r/D) portion also represents the decimal portion of the number. To illustrate this look at 7(1/2). This is 7.5 where the .5 comes from the (1/2)

* Note given D, we can sometimes determine whether a number can be represented as a terminating decimal:

#107 OG11: Is r/s a terminating decimal?
(2) s = 4

--> Recognize that r/s can be represented as r = sQ + R, where s is the divisor, Q is the quotient and R is the remainder. We know that 0 <= R < s (stated above), so given s = 4, we know the possible values for R: 0, 1, 2, 3. The decimal portion of the number is (R/s) so the possible decimal values are 0/4, 1/4, 2/4, 3/4, which is .0, .25, .5, .75.

Let's look at another example:

#148 OG11: What is the tens digit of positive integer x?
(1) x divided by 100 has a remainder of 30

--> Convert to the equation: x = 100q + 30. Choose values for q:

q = 1: x = 100 + 30 = 130
q = 2: x = 200 + 30 = 230
q = 3: x = 300 + 30 = 330
Sufficient.

(2) x divided by 110 has a remainder of 30

--> Convert to the equation: x = 110q + 30. Choose values for q:

q = 1: x = 110 + 30 = 140
q = 2: x = 220 + 30 = 250
q = 3: x = 330 + 30 = 360
Not sufficient.

Now back to N = Dq + r.

We know from this equation that N is not divisible by D because of the remainder r.

# 12 Paper Test 14, Section 7:

If x is an integer and y = 3x + 2, which of the following CANNOT be a divisor of y?

(A) 4
(B) 5
(C) 6
(D) 7
(E) 8

--> y cannot be divided by 3 because of the remainder 2. Which of the answer choices are dependent on division by 3? Only 6 so that is the correct answer.

So as you can see, this equation can be used to give you extra insights into certain classes of problems (namely number properties, but it may also appear in something like probability). For an example of a probability question, take a look at this little twist to the last problem above:

If x is an integer and y = 3x + 2, what is the probability that y is NOT divisible by a number chosen randomly from a set of the first 10 integers greater than 0? (I just made this question up on the spot)

Answer:
* Set of first 10 integers greater than 0: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
* y NOT divisible by 3, 6, or 9
* 3 choices/10 total numbers = 30%

How do you recognize when to use this equation?
1) Number property problem or probability problem that contains a variation of this equation.
2) Questions that involve remainders

So that's all. If anyone finds anymore interesting applications of this equation, please let me know.

mayonnai5e · Posted: Sat Sep 22, 2007 9:51 am Post subject:

Took my first MGMAT CAT and man was it brutal. The math was just ridiculous! The last few CATs I've taken were PR and PowerPrep and the math pales in comparison. The questions were just layered with complexity and often were time-consuming. About halfway through the math, I thought to myself, "make it stop, please make it stop...." =P

After the math, my brain felt fried - it was kind of like taking a midterm or final in college all over again...except that there was another 75 minute portion coming up! Well at least I stuck with it and finished the exam without hitting the pause button.

As far as timing goes, I had to guess from 30 to 37 on Math and 38 to 41 on V. That's about 11 problems guessed, which is an improvement, but still not satisfactory.

Anyways, my score was 650 Q40 and V38, which is right in line with the last few scores I've achieved:

GMAT Paper Test #14 680
GMAT Paper Test #55 660
PR CAT 3 660
MGMAT 1 650

My V score was a bit disappointing because I thought I was doing fairly well and was generally confident on most answer choices.

When will I break the coveted 700 mark?

mayonnai5e · Posted: Sun Sep 23, 2007 2:37 pm Post subject:

I did questions 76-116 of the RC set in OG11 under timed conditions. I started off giving myself 3 minutes per passage + 2 minutes per questions, but I found that too be too lenient so I lowered the time to 1.5 minutes per question. I got all of them right except question 116 - that's a 97.5% hit rate. =)

mayonnai5e · Posted: Mon Sep 24, 2007 6:12 am Post subject:

I've taken several different CATs thus far in my practice. Here are my thoughts on them:

PowerPrep
- First CAT I took
- Felt the math was not too tough - I didn't see too many problems where I just had no clue how to solve it, but the difficulty progression was slow
- Verbal was difficult to read
- This program does not handle screen resolution well - on my 20 inch widescreen monitor, the program changed my default resolution and made it very hard to read the Verbal portions

GMATPrep
- Undeniably the best CAT out there as it is the official practice CAT
- The math got tough very quickly so I knew I was in the upper bin territory, which really upped my anxiety and nervousness and took me out of my "comfort" zone.
- Verbal was verbal. I hadn't studied verbal at all when I took my first GMATPrep CAT so wasn't expecting anything different from PowerPrep and didn't score any differently

PR
- My scores with these CATs have been in the same range as the GMATPrep and PowerPrep exams, but I think there are significant drawbacks to this CAT
- The difficulty progression is very, very slow. This makes it difficult to reach the more difficult questions because you have to get many correct in a row (I had sequences of 9-13 correct in a row on several CATs). This does not simulate the real CAT, which very quickly pushes you to your limits. On GMATPrep, I found myself out of my "comfort zone" around question 15 whereas on the PR CATs I usually didn't hit that point until question 25.
- There seems to be a huge penalty for getting an answer wrong in the first questions. This combined with the slow difficulty progression means that if you get one or two of the first questions wrong, you'll be digging yourself out of a very large hole. I think PR followed their own advice too much and purposely adjusted their algorithm to penalize takers severely for questions missed at the beginning.
- My opinion: This CAT is flawed in the difficulty progression of the algorithm and the scoring algorithm

MGMAT
- These are the closest CATs I've taken to GMATPrep.
- At around question 10 on the math, I was already seeing questions for which I had no idea how to solve correctly.
- My stress/anxiety levels on this CAT were similar to those I experienced on GMATPrep.
- The Verbal section seem a bit off from the OG11 problems. I feel like the verbal section was designed to match the ideas taught in the MGMAT books instead of matching the OG11 questions.

Overall, GMATPrep is the best with MGMAT following behind. The reason is because I felt the MGMAT CATs pushed me like the GMATPrep did. The questions became difficult very quickly, and I was constantly stressed. If I were taking the real CAT, I imagine I would feel the same level of anxiety as I felt on the MGMAT CAT.

Oh, while I'm on the topic of tests, I've also taken some of the paper tests, but I found them to be unrepresentative because 1) they're non-adaptive 2) they seem to contain more easy to middle difficulty questions 3) a large portion of the old problems are included in the OG guides. As a result, I do not recommend them for gauging your score level; they are better for practice or to practice timing.

mayonnai5e · Posted: Mon Sep 24, 2007 12:02 pm Post subject:

CR 9/8/07:

Two specific ways to weaken:
1) Provide alternative explanation
2) Weaken the analogy is an analogous situation is put forth

9/13/07:
Assumptions - are premises that must support conclusion
--> eliminate choices that do not support conclusion (out of scope/irrelevant)
--> assumption must be true

LOOKOUT - for keywords that qualify/limit/narrow a statement - they can narrow the scope of the conclusion and provide a way to attack argument
--> "the company will see an IMMEDIATE cost benefit"
--> show that the company's benefit will not be immediate

WATCH OUT - for answer choices that simply restate a premise
stimulus: "...country x has experienced similar conditions"
answer choice: "both have experienced drought conditions"

CONTRADICTIONS - if an answer choice contradicts a premise, it is most likely wrong since premises must be true.
#101 CR OG11 (inference type)
"...but such an action would be likely to cause international discord" <-- premise!
(b) "As long as international opinion is unanimously against patria..." <-- unanimously implies agreement but premise states there will be discord
(e) "for a blockade of Patria's ports to be successful, international opinion must be unanimous"

TIME WASTER - rereading question stems that are long in order to fully understand what is being asked
--> look for the basic question type and go straight to the stimulus
--> long question stems often appear in stimuli with two opposing sides and you are asked to look for something relating to one side

Assumptions - premise must not be out of scope
--> e.g. "Sandactulus" and birds
--> answer choice: "...all creatures that fly..." (addresses more animals than stimulus discusses)

Statistics - watch out for stimuli with rates/percents/totals
--> focus only on the quantity that is relevant
--> #92 OG11 : ....10 cents per miles
(b)...the total number of trips...
(c) .. avg length of trips
(e) ...total distance...(correct...stimulus deals with money and distance)

Assumptions - Eliminate answer choices that presuppose conclusion. Assumption supports conclusion - the conclusion cannot already be true.

Statistics - Note the difference between a specific portion of a larger population vs the average for that population --> the specific portion is included in the calculations for the average
--> #103 OG11: "...the average life span [of Louisianans]"
(c) 25% of all Louisianans
(d) average life expectancy has risen
-->both are included in the calculations used to determine avg

REMEMBER - on long arguments with multiple sentences, do not overlook beginning sentences as crucial information is sometimes provided

WEAKEN - another important way to weaken (usually found on hard CR): weaken assumptions presupposed by argument
--> harder because you must find the assumption first then weaken it.

mayonnai5e · Posted: Mon Sep 24, 2007 2:11 pm Post subject:

Finished RC section of OG11. I have now finished the CR, DS, and RC sections. My hit rates are:

CR - 89%
DS - 81%
RC - 91%

Those don't really mean much in the end - what matters is whether I can apply what I know under test conditions with the associated stress, anxiety, and time pressure.

mayonnai5e · Posted: Thu Sep 27, 2007 4:41 pm Post subject:

Updates:

1) Completed SC section of OG11 - hit rate 88%

2) Completed second MGMAT CAT. I took this over the past two days (Q first then V) because I cannot take a full CAT after 8 hours of work (that wouldn't be representative of testing conditions anyways - who takes the official CAT after 8 hours of work?)
- SCORED MY FIRST 700 on a CAT. 42 Q 42 V
- I thought the Q was just ridiculous again. I saw some word problems that were like 4 or 5 sentences long. They looked like CR questions. I guessed immediately and moved on - if I had tried to solve it I would have just wasted precious time.
- timing: guessed on last 4 of Q, guessed on only 1 in V
- V was pretty straight forward; I saw a few CR and RC questions that were hard, but I just guessed and moved on. I know my V is strong so if I get one wrong, I can probably make it up later.

3) RC notes 9/25/07:

Main Idea - Look in three places: 1) first paragraph 2) last paragraph and if you can't figure it out, 3) quickly scan all paragraphs and logically organize them together to create a main idea

WATCH OUT for qualifying phrases that reverse what the passage states
--> #77 OG11: (B) "concentration of serotonin in the blood before [meals]"
--> passage discusses the concentration of serotonin after meals

Experiments - in scientific passages, be sure to distinguish between the hypothesis and the results/conclusion --> results cannot have been positively known before experiment (watch out for answer choices that assume the conclusion)

"According to" - First, look for keywords in the question stem to determine the relevant portion of the text. Second, look for keywords in the relevant text to eliminate incorrect answers.

Time - in passages where dates and time is discussed, mentally organize relevant dates and time.
e.g. experiments with subsequent experiments
e.g. economic changes followed by social changes and vice versa
--> some incorrect answer choices may reverse time order and thus make the question wrong even though relevant topics are discussed

Specific VS Group - Note when the subject of the passage is a specific part of a larger group --> WATCH OUT for answers that generalize from the specific part to the entire group
#84 OG11 (inference):
(c) the rats would produce neurotransmitters other than serotonin
--> serotonin is the only neurotransmitters discussed so we cannot generalize to a larger group

#80 OG11:
(d) the number of neurotransmitters of any kind that the rats will produces

--> the passage in this case says, "we have discovered that production...of the neurotransmitter serotonin"

Statistics - is the data representative?
#114 OG11 (weaken):
--> author states, "as much as 90 percent of the mass of the universe is not radiating..."
--> if we can prove the data the author studied is not representative then we can weaken (similar to CR strategy)

DO NOT forget the original idea that introduced the main topic of a passage - this occurs when an idea is first discussed that leads into the main idea (the intro idea is usually found in the first paragraph)
--> intro provides clues for inferences, etc
#121 OG11:
Main topic: oligosaccharins (specific type of regulatory molecule)
Intro idea: gene complements in plants and how they are controlled

"According to" - If you find the exact match and you're confident it's right, answer it and move on quickly. Don't waste time reading the other choices (this is counter to the rule that you should always read answer choices, but if timing is an issue..)

Guest · Posted: Thu Sep 27, 2007 4:58 pm Post subject:

Congrats on the CAT score!

mayonnai5e · Posted: Sun Sep 30, 2007 1:51 pm Post subject:

Completed MGMAT CAT #3. This CAT was completed all at once unlike my last CAT, which I completed over two days.

690 Q45 V39

Thoughts:
1) My Q went up which is good considering I've been focusing on Q for the past week. I have some very specific areas of Q that I relaly need to increase my speed in (e.g. word problems with rates and percentages).
2) My V went down which is not so good since I think my verbal understanding is decent
3) Timing: guessed on about 3-4 on each section. This is worst than my previous CAT. I need to learn to recognize more quickly harder questions that I cannot possibly complete in 2 minutes.
4) Overall score is still good once I factor in standard deviation.
5) I looked through my verbal and I missed 17 questions total. Out of those 17, all but 2 were 700-800 level. I don't quite understand why my V was only 39 when I mostly missed 700-800 level questions and got almost every 500-700 level question correct. Anyone have any thoughts on this?

Overall feeling: Satisifed because I was scared going into this CAT that my score would drop significantly and that the last 700 was just a fluke.

MGMAT CATs:
1 650 Q40 V38
2 700 Q42 V42
3 690 Q45 V39

Guest · Posted: Sun Sep 30, 2007 1:58 pm Post subject:

Great seeing your progress, congratulations!

mayonnai5e · Posted: Sun Sep 30, 2007 2:01 pm Post subject:

mayonnai5e · Posted: Sun Oct 07, 2007 12:15 pm Post subject:

Well I haven't posted anything in a week because I've been really trying to hard focus on my studying rather than trolling through these forums. I took my second GMATPrep today and scored decently well:

710 Q42 and V45

I missed 16 out of the 37 and had to guess on the last 2 or 3.
I missed 7 out of the 41 V and had to guess on the last 4.

However, I did see one RC passage from the OG and knew all the answers for that passage so I answered them fairly quickly which obviously skewed my V timing.

I'm really disappointed in my Q score because I'm an engineer and because my MGMAT Q scores have been progressively getting better (supposedly the Q on those CATs are harder then the official Q)

Anyways my progress is as follows:

MGMAT 1 Q40 V38 650
MGMAT 2 Q42 V42 700
MGMAT 3 Q45 V39 690
GMATPrep 2 Q42 V45 710

Looking through the Q questions that I got wrong, a majority of them were ones where I just guessed and moved on although I did notice 1 or 2 really careless mistakes. I have only one week left so I think I will focus on the math portion.

I'm not 100% sure how to proceed, but going over the OG problems that I missed is definitely necessary. If anyone has any suggestions on how I can bump my Q score in a week's time please do let me know.

mayonnai5e · Posted: Sun Oct 07, 2007 3:58 pm Post subject:

I'm quite happy with my Verbal on GMATPrep 2. I got 5 right in a row, then missed #6, then got 9 right in a row and missed #16. Then I got 15 right in a row and missed #32. Questions 32 through 36 was the multinational corp question from OG11, which were the only repeats I saw. I missed 4 at the very end because I ran out of time. My timing is still an issue, but my accuracy seems to be right on the money.