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the way i saw this this was noticed the term -2(s - 4)^2 is always negative, and only 0 when s = 4. which means the largest value of that term = 0 when s = 4. 32 is of course constant so the P(s) function achieves its maximum at s = 4. just different wording than above, but through a different lens.

by el_torero

Tue Mar 30, 2010 10:06 pm
Forum: Problem Solving
Topic: # of Passengers
Replies: 8
Views: 1404

here's my reasoning: start by doing a prime factorization of 144: 144 = (2^4)*(3^2) (1) if X is divisible by 144, then X = M*(2^4)*(3^2) for some positive integer M. therefore, we're guaranteed that 2 and 3 are two of prime factors of X. (2) if X^(1/3) is an integer, then X's prime factors must have...

by el_torero

Tue Mar 30, 2010 8:57 pm
Forum: Problem Solving
Topic: Can someone answer this with explanation?
Replies: 3
Views: 1524
by el_torero

Tue Mar 30, 2010 7:26 pm
Forum: Problem Solving
Topic: 2 equations, 2 unknowns
Replies: 2
Views: 974

2 equations, 2 unknowns

i have a question that reduces to the following:

22S + 16B = 650
8S + 32B = 760

what is S - B?



of course, one way is to do substitution, etc. however, does anyone have a really smooth way to do this?

by el_torero

Tue Mar 30, 2010 6:50 pm
Forum: Problem Solving
Topic: 2 equations, 2 unknowns
Replies: 2
Views: 974

here's my take at it: to find P(jim wins), lets figure out all of his winning situations: (1) Jim chooses rock; renee chooses scissors (note their decisions are independent) (2) Jim chooses paper, renee chooses rock (3) Jim chooses scissors, renee chooses paper So P(Jim wins) = P(1) + P(2) + P(3). t...

by el_torero

Fri Mar 26, 2010 2:18 pm
Forum: Problem Solving
Topic: Manhattan GMAT Probability
Replies: 3
Views: 2573

nice save. that last amount of information (that 3 is in P) is super important. @eaakbari: i do agree that without the new information, the answer should be E and the reason why is we just don't know if 3 is in the set, or if 0 is in the set, or any multiple of 3 is in the set. in order to confirm t...

by el_torero

Fri Mar 26, 2010 1:53 pm
Forum: Data Sufficiency
Topic: hard question
Replies: 20
Views: 2691

i agree with neoreaves. just to clear up, we want to find: P(roar or rain) = P(roar) + P(rain) - P(roar AND rain) (1) makes P(roar AND rain) = 0, but we still need to find P(roar) + P(rain) (2) gives us a relationship between roars and rain, but we still need to find at least one of those unknowns t...

by el_torero

Fri Mar 26, 2010 1:46 pm
Forum: Data Sufficiency
Topic: Roar and Rain
Replies: 4
Views: 2232

i nice rule to use here that i picked up in someone else's post is that 2^10 = "binary 1000" = 1024, an easy way to remember a huge power of 2. this helps you deduce what n is really quickly.

by el_torero

Fri Mar 26, 2010 1:28 pm
Forum: Data Sufficiency
Topic: Probablity
Replies: 10
Views: 1332

i agree with the above posts. E is the right answer and here's why: once you derive x+y < 73/72, it becomes clear you can come up with two numbers that are either < 1 (i.e. negative numbers for both x and y) or a pair of numbers whose sum is greater than 1 AND less than 73/72 (i.e. 729/720). gg gl

by el_torero

Thu Mar 25, 2010 4:56 pm
Forum: Data Sufficiency
Topic: x and y
Replies: 7
Views: 1207

No specific examples. Just wondering how to correctly use both types of idioms.

Thanks for the reply!

by el_torero

Tue Mar 16, 2010 8:07 pm
Forum: Sentence Correction
Topic: idiom: discouraged from
Replies: 3
Views: 2297

idiom: discouraged from

The idiom"discouraged from" appears on a bunch of lists of idioms used on the GMAT.

However, when is it correctly used, and when should you use "discouraged by"?

Thanks!

by el_torero

Mon Mar 15, 2010 9:43 pm
Forum: Sentence Correction
Topic: idiom: discouraged from
Replies: 3
Views: 2297