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Quantitative Review DS #116

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Source: — Data Sufficiency |
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by jaiswaln » Fri Jan 04, 2008 6:49 am
Answer is A.

2 * x^0.5 can only be an integer if x^0.5 is an integer.
( options A, D are only possibility now)


where as 3^0.5 * x^0.5 doesnt tell us anything thing about x^0.5 as 3^0.5 is not an integer hence the product is non integer.

This rules out D.
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by gguy » Sun Jan 06, 2008 1:25 am
Yes, I misunderstood the Q. I was attempting to prove that X is an integer while we were asked to prove that sqrt(x) is an integer.
My bad. thanks
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by gmatguy16 » Sun Jan 06, 2008 9:56 am
i am not sure why is the answer a,if we know that (4x)^1/2 is an integer why do we know that x^1/2 is an integer.. say (4x)^1/2 = 15 (integer) in that case x^1/2 = 7.5 which is not an integer
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by Argen » Mon Jan 07, 2008 9:15 am
I agree that it'd be E, because statement 1 says 2*sqrt(x) is an integer. Let 2*sqrt(x)=3, so sqrt(x)=1.5 which is not an integer. However if x is a perfect square then sqrt(x) is an integer.
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