number properties

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Source: — Data Sufficiency |

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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
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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.
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