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Integers

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by Akansha » Mon May 23, 2011 9:16 pm
n and y are positive integers and 450y = n3, which is an integer?
y / 3 * 22 * 5
y / 32 * 2 * 5
y / 3 * 2 * 52
a. None
b. I
c. II
d. III
e. I, II, III

OA is B

I had difficulty in understanding this question. Need help.
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Source: — Problem Solving |

by Anurag@Gurome » Mon May 23, 2011 9:31 pm
Akansha wrote:n and y are positive integers and 450y = n3, which is an integer?
y / 3 * 22 * 5
y / 32 * 2 * 5
y / 3 * 2 * 52
a. None
b. I
c. II
d. III
e. I, II, III

OA is B

I had difficulty in understanding this question. Need help.
450y = n^3
450 = 2 * 3² * 5², so 2 * 3² * 5² * y = n^3
For the above equation to be true, y = 2² * 3 * 5 (since the right hand side is the power of 3)
So, I is true.

The correct answer is B.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
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