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How many of the factors of 72 are divisible by 2

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by Anju@Gurome » Mon Apr 22, 2013 11:54 am
guerrero wrote:How many of the factors of 72 are divisible by 2?
72 = (2^3)*(3^2)

Even factors of 72 will contain at least one 2 in it but it may or may not contain 3.
So, any even factor of 72 will contain either 2^1 or 2^2 or 2^3 and either 3^0 or 3^1 or 3^2.
So, number of even factors of 72 = 3*3 = 9

The correct answer is E.
Last edited by Anju@Gurome on Mon Apr 22, 2013 11:57 am, edited 1 time in total.
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by Brent@GMATPrepNow » Mon Apr 22, 2013 11:56 am
guerrero wrote:How many of the factors of 72 are divisible by 2?

A. 4
B. 5
C. 6
D. 8
E. 9
what's been tested in this question and the approach ?

thanks in advance !

OA E
Rewording: How many factors of 72 are even?

The relatively small answer choices suggest that listing and counting will be pretty fast.

Factors of 72: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72

So, there are nine such numbers.

Answer = E

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Brent
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