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GMAT Quant Integer Prob

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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GMAT Quant Integer Prob

by kutumalu » Tue Jun 28, 2011 11:30 pm
Hey guys, I'm trying to do some practice probs and I came across this question:

"what is the smallest positive integer k such that the product 1575 x k is a perfect square?"

(A) 7
(B) 9
(C) 15
(D) 25
(E) 63

I'm not sure of how to approach this question so i'd really appreciate any help/input from you guys!
I'd like to know if there's a trick to tackle such questions on the GMAT. I believe there is and I know that I NEED to learn it ASAP!

thank you in advance guys! :)

cheers
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by Frankenstein » Tue Jun 28, 2011 11:41 pm
Hi,
First express the number as product of prime factors in every such problem
1575 = 25*63 = 3^2*5^2*7
For the number to be perfect square all the powers should be even numbers.
power of 3 is 2(even)
power of 5 is 2(even)
power of 7 is 1(odd)
So, in order to make power of 7 even we need to multiply the number by 7.

Hence, A
Cheers!

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by kutumalu » Tue Jun 28, 2011 11:59 pm
Hey there

Thanks a lot! I got it :)
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by kutumalu » Wed Jun 29, 2011 12:05 am
Hey there

Thanks a lot! I got it :)
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