Integers

This topic has expert replies
User avatar
Senior | Next Rank: 100 Posts
Posts: 56
Joined: Wed Sep 01, 2010 10:04 am
Thanked: 1 times
Followed by:20 members

Integers

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.
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

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.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/