Official Guide Orange Data Sufficiency #146

fernandonefro wrote:Is n an interger?

(1)n to the power of 2 is an interger
(2)The root of n is an interger

Anybody knows how to explain the (1) better than the Oficcial Guide?
I did not understand...

the answer is B.

n to the power of 2 is basically n^2. If n^2 is an integer, it doesnt necessarily mean that n is an integer. Eliminate (1)

If root of n is an integer, then n will also be an integer.

fernandonefro wrote:Is n an interger?

(1)n to the power of 2 is an interger
(2)The root of n is an interger

Anybody knows how to explain the (1) better than the Oficcial Guide?
I did not understand...

1. n*n = an integer.
If n*n = 4, n = 2 or -2 and is an integer.
However, n can be sqrt(2). Then n*n = sqrt(2) * sqrt(2) = 2 = an integer. But sqrt(2) is not an integer.
NOT SUFFICIENT.

2. sqrt(n) = integer
If you square both side, n = square of an integer.
Square of an integer is always an integer since you are multiplying two integers.
SUFFICIENT.

Answer is B.


Also, when you are in doubt, try to post what part of a concept/problem you do not understand. That way, somebody can elaborate on that specific point with more detail.

thank you for this answer!! i fogot the n could be = the square root of a number. was killing me.