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MGMAT - Properties

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Ves
 Post subject: MGMAT - Properties
 Post Posted: Sun Jan 04, 2009 10:17 pm 
If n and y and both positive integers, and 450y=n^3, which of the following must be an integer:

I. y/(3)(2^2)(5)


II. y/(3^2)(2)(5)

III. y/(3)(2)(5^2)


Ans: I only

Can you please explain the answer?

Thanks
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Ves
 Post subject:
 Post Posted: Mon Jan 05, 2009 9:17 am 
Source is GMAT Prep
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aryan
 Post subject: Soln explained
 Post Posted: Mon Jan 05, 2009 10:08 am 
since n^3=450y
n=cube root(2*5^2*3^2*y)

as n is integer so y=2^2*5*3 it is minimum there may be other value which must be multiple of 60.
hence the ans is y/3.4.5
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Ves
 Post subject:
 Post Posted: Mon Jan 05, 2009 10:53 am 
Thanks a lot Aryan!
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RonPurewal
 Post subject:
 Post Posted: Fri Jan 09, 2009 9:26 am 
Offline
ManhattanGMAT Staff


Posts: 7146
people!
"450y" is the world's greatest search term. type it into the box and watch at least 3 old threads come up.
i understand that the search box is obstreperous at times, especially when the search string contains rather generic terms (a fair number of math problems don't really contain anything other than numbers and letters, making searches difficult), but you should have no trouble finding this one.

http://www.manhattangmat.com/forums/if- ... t4311.html

http://www.manhattangmat.com/forums/if- ... -t279.html
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