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Manhattan Challenge Problem

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Saurabh Malpani
 Post subject: Manhattan Challenge Problem
 Post Posted: Sat Apr 28, 2007 8:15 pm 
12/01/03
Question
How many numbers that are not divisible by 6 divide evenly into 264,600?

(A) 9
(B) 36
(C) 51
(D) 63
(E) 72


I understand the the solution except the last part where the answer is arrived at by Subtracting the 81 from 144 (I mean I understand what are the steps followed but I don't understand why My answer is wrong)

My Apporach was:

As known that to be multiple of 6 we need to have atleast one 2 and one 3. In my apporach I try to calculate, just as we do in Combinations,the number of factors when I have ONLY 2s and Only 3s in additon to 5 and 7
2^4 * 5^2 *7^2 --- i.e multipy 3*3*3 =27

2^4 * 5^2 *7^2------- i.e multipy 3*3*3 =27

Sum them up I get 54.

So what's wrong with my apporach..???
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Saurabh Malpani
 Post subject:
 Post Posted: Sat Apr 28, 2007 8:18 pm 
Well as I was typing the problem the solution clicked to me the problem in my apporach is that i am not adding 7^2 * 5^2---3*3=9 . 9+ 54 =63 which is the correct answer.

Thanks
Saurabh Malpani
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StaceyKoprince
 Post subject: ManhattanGMAT Challenge Problem Dec 1 2003
 Post Posted: Sun Apr 29, 2007 11:35 pm 
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ManhattanGMAT Staff


Posts: 6077
Location: San Francisco
Great! It's always the best when you figure it out for yourself! (And do remember - the challenge problems are likely to be harder than anything, or almost anything, you'll see on the test. Just make sure you've mastered absolutely everything else - otherwise, it's not a wise use of your time to use these extensively.)

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Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT
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atayamir
 Post subject: Re: Manhattan Challenge Problem
 Post Posted: Mon Feb 28, 2011 9:18 pm 
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Students


Posts: 1
i don't get it?
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jnelson0612
 Post subject: Re: Manhattan Challenge Problem
 Post Posted: Thu Mar 03, 2011 10:11 am 
Offline
ManhattanGMAT Staff


Posts: 1857
There is an explanation at this link: how-many-numbers-that-are-not-divisible-t4234.html

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Jamie Nelson
ManhattanGMAT Instructor
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