Jeff Miller

GMAT OFFICIAL GUIDE DS – If n is an inte…

If n is an inte…

Solution:

We need to determine whether n is an integer.

Statement One Alone: 

n^2 is an integer.

If n^2 is an integer, n could be an integer or a non-integer. For instance, if n^2 = 4, then n is an integer (since n = 2 or -2). However, if n^2 = 5, then n is not an integer (since n = √5 or -√5).

Statement one is not sufficient to answer the question. We can eliminate answer choices A and D.

Statement Two Alone: 

√n is an integer.

In order for √n to be an integer, n must be an integer. This is because n = (√n)^2 and any integer, when it is squared, is also an integer. Statement two is sufficient to answer the question.

Answer: B

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