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integer squares

by rbales » Thu Nov 10, 2011 2:21 pm
There's a question in the OG data sufficiency section that is posed as such:

169. Is n an integer?

I. n^2 is an integer
II. sqrt(n) is an integer

I thought the answer was D, but apparently only II is sufficient. The explanation of the insufficiency of I states that the square of a non-integer can be an integer, but it fails to give any examples. What is an example of a non-integer whose square is an integer?
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by neelgandham » Thu Nov 10, 2011 2:52 pm
rbales wrote: only II is sufficient. The explanation of the insufficiency of I states that the square of a non-integer can be an integer, but it fails to give any examples. What is an example of a non-integer whose square is an integer?
1)n^2 is an integer

If n^2 = 1, then n = 1 or -1 and n is an integer
If n^2 = 2, then n = √2 or -√2 and n is NOT an integer
If n^2 = 3, then n = √3 or -√3 and n is NOT an integer

So, the statement alone is insufficient to answer the question. Let me know if you are not convinced :)
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by vaibhavgupta » Thu Nov 10, 2011 4:30 pm
rbales wrote:There's a question in the OG data sufficiency section that is posed as such:

169. Is n an integer?

I. n^2 is an integer
II. sqrt(n) is an integer

I thought the answer was D, but apparently only II is sufficient. The explanation of the insufficiency of I states that the square of a non-integer can be an integer, but it fails to give any examples. What is an example of a non-integer whose square is an integer?
At the risk of generalizing:

In most of the scenarios, n2 is something, will not assure that is also that. there are various scenarios which are present and need to be looked at !

Hence, B is the answer! :)
If OA is A, IMO B
If OA is B, IMO C
If OA is C, IMO D
If OA is D, IMO E
If OA is E, IMO A

FML!! :/
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