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number properties

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Source: — Data Sufficiency |

by Brent@GMATPrepNow » Wed Jan 25, 2012 7:33 pm
sud21 wrote:m and n are integers, is m^n an integer?
1) n^m is positive
2) n^m is an integer
This one is best solved using some convenient counter-examples.

Statement 1:
There are several possible values for m and n that satisfy the condition that n^m is positive.
Here are two such cases:
Case a: m=1 and n=1, in which case m^n is an integer
Case b: m=2 and n=-1, in which case m^n is not an integer
Since statement 1 does not allow us to answer the target question with any certainty, it is NOT SUFFICIENT

Statement 2:
There are several possible values for m and n that satisfy the condition that n^m is an integer.
Here are two such cases:
Case a: m=1 and n=1, in which case m^n is an integer
Case b: m=2 and n=-1, in which case m^n is not an integer
Since statement 2 does not allow us to answer the target question with any certainty, it is NOT SUFFICIENT

Aside: Notice that I used the same values for m and n to show that each statement is NOT SUFFICIENT. As such, the statements combined are NOT SUFFICIENT, which means the answer is E

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by Anurag@Gurome » Wed Jan 25, 2012 7:58 pm
sud21 wrote:m and n are integers, is m^n an integer?
1) n^m is positive
2) n^m is an integer
For two integers m^n will be also integer only if n is a positive integer. So the question boils down to Is n a positive integer?

None of the statements individually or combined together allow us to conclude that n is a positive integer. Hence, both statements together is also not sufficient to answer the question.

The correct answer is E.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

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