Search found 103 matches
ssmiles approach is the quickest for these types of problems. If you don't feel comfortable with the formulas/approach, check out Manhattan GMAT's Number Properties book. It's a great book.
- by raleigh
Thu Jun 18, 2009 9:45 am- Forum: Problem Solving
- Topic: If a equals the sum of the even integers...
- Replies: 3
- Views: 9147
Approach this problem like you would approach any problem with exponential terms with the same base -- factor it. Note that every term is a power of 2. You can factor out one 2 from the sum, but that doesn't buy us much. If we combine 2 + 2 = 2*2 = 2^2, we can now factor out a factor of 2^2. After c...
- by raleigh
Thu Jun 18, 2009 9:37 am- Forum: Problem Solving
- Topic: GPREP 2+2+(2^2)+(2^3)+(2^4)+(2^5)+(2^6)+(2^7)+(2^8)
- Replies: 8
- Views: 10323
The question says approximately, right? Since each term is base 10, we can factor the numerator and the denominator. Since it's addition/subtraction we have no other way of combining terms. Numerator: (10^8 - 10^2) = 10^2(10^6-1) Denominator: (10^7 - 10^3) = 10^3(10^4-1) So (10^8 - 10^2) / (10^7 - 1...
- by raleigh
Thu Jun 18, 2009 8:24 am- Forum: Problem Solving
- Topic: GMATPrep Question Help...
- Replies: 6
- Views: 1460
I'm pretty certain the latest edition is only available on the MGMAT site. The number properties book is good. I was in a similar position. 3 chapters in it helped me out a lot.
- by raleigh
Wed Jun 17, 2009 8:54 pm- Forum: Problem Solving
- Topic: Properties of numbers
- Replies: 4
- Views: 1254
Did you write this problem incorrectly? Should there be paranethesis or anything? I approximate this to be 10^7.
- by raleigh
Wed Jun 17, 2009 6:25 pm- Forum: Problem Solving
- Topic: GMATPrep Question Help...
- Replies: 6
- Views: 1460
It is most likely caused from you being unfamiliar with the problem type. Data sufficiency problems seem weird at first. What is your strategy for approaching data sufficiency problems? And remember, that you don't have to solve the problem, you just have to determine whether or not you have enough ...
- by raleigh
Wed Jun 17, 2009 2:01 pm- Forum: Data Sufficiency
- Topic: OG 12 DS Difficulty level
- Replies: 4
- Views: 1841
A big problem of mine isn't carefully reading the whole problem and picking out all the information. We're pressed for time that we try to get to our calculations as fast as possible. I'm trying to slow down when I first look at the problem so that way I don't miss anything. They always seem to have...
- by raleigh
Mon Jun 15, 2009 1:21 pm- Forum: Problem Solving
- Topic: Another Challenge Distance Problem
- Replies: 7
- Views: 2107
Very intuitive way to look at the problem. Good work. I see any sort of projectile motion and I instinctively think calculus 
- by raleigh
Sun Jun 14, 2009 6:46 pm- Forum: Problem Solving
- Topic: An object thrown directly upward
- Replies: 6
- Views: 6634
Factor a ten out of the denominator and it will cancel leaving you with 30,000 in the numerator. The problem asks for the ratio in reduced form. Otherwise, you could multiply by 10/10 as many times as possible to inflate the numerator.
- by raleigh
Sun Jun 14, 2009 6:45 pm- Forum: Problem Solving
- Topic: Another Challenge Distance Problem
- Replies: 7
- Views: 2107
Ave = total distance / total time Ave = 100/ x/60 + 100-x/50 = 100/ 50x + 6000 - 60x / 3000 this is the second difference. Your problem that you did not use the definition of average rate correctly. You added the average rate for each segment of the trip. The average rate is total distance / total ...
- by raleigh
Sun Jun 14, 2009 5:31 pm- Forum: Problem Solving
- Topic: Another Challenge Distance Problem
- Replies: 7
- Views: 2107
I don't use a formula for permutations. Refer to the permutation problem where we have 10 people, and we want to know how many possibilities for the pres/vice-pres/treasurer there are. Here is how I would solve this: There are 10 choices to fill the president position. Now there are 9 remaining choi...
- by raleigh
Sun Jun 14, 2009 4:59 pm- Forum: GMAT Math
- Topic: Permutations/Combinations - always get them mixed up!?
- Replies: 4
- Views: 1603
This isn't a GMAT problem, this is a calculus problem. We know that when an object reaches it's maximum height, it's velocity is zero. So to find the time the object is at it's maximum height, we take the derivative and set it equal to zero. h'(t) = -32(t-3) Set it equal to zero and solve for t and ...
- by raleigh
Sun Jun 14, 2009 4:03 pm- Forum: Problem Solving
- Topic: An object thrown directly upward
- Replies: 6
- Views: 6634
This is a problem where it helps to plug in a value. Since the first part of the trip is x percent of the distance, choosing the distance of the trip to be 100 miles means that the distance traveled at the first rate will be x. So let D = 100 miles. Then she traveled x miles at 50 miles per hour. D ...
- by raleigh
Sun Jun 14, 2009 3:42 pm- Forum: Problem Solving
- Topic: Another Challenge Distance Problem
- Replies: 7
- Views: 2107
In permutation problems, order MATTERS. These are problems like "There are 10 people in a group. One person will be selected as president, one person will be selected as vice president, and another for treasurer. How many different choices can be made to fill these positions?" In a combina...
- by raleigh
Sun Jun 14, 2009 3:25 pm- Forum: GMAT Math
- Topic: Permutations/Combinations - always get them mixed up!?
- Replies: 4
- Views: 1603
y=3x+2 containing the point (r,s) means that s = 3r + 2. (1) Tells us that 3r + 2 - s = 0 OR 4r + 9 - s = 0. 3r + 2 - s = 0 gives us s = 3r + 2. But this can also be satisfied from s = 4r + 9 (from 4r + 9 - s = 0) So this is not sufficient. (2) Similarly, we get 4r - 6 - s = 0 OR 3r + 2 - s = 0. Sol...
- by raleigh
Sun Jun 14, 2009 10:55 am- Forum: Data Sufficiency
- Topic: GMAT Prep
- Replies: 1
- Views: 981