Help with question from GMAT software practice test!

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houstonrockets16: Junior | Next Rank: 30 Posts; Posts: 26; Joined: Mon Feb 02, 2009 4:45 pm; Thanked: 1 times

by houstonrockets16 » Sun Jun 07, 2009 5:05 pm

20)

If X and Y are integers greater than 1, is X a multiple of Y?

1) 3Y^2 + 7Y = X
2) X^2 - X is a multiple of Y.

Thanks in advance!

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Source: Beat The GMAT — Data Sufficiency | Sun Jun 07, 2009 5:05 pm

Claret: Senior | Next Rank: 100 Posts; Posts: 97; Joined: Sat Jun 06, 2009 10:48 pm; Thanked: 4 times

by Claret » Sun Jun 07, 2009 5:11 pm

Ans (A) ?

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ssmiles08: Master | Next Rank: 500 Posts; Posts: 472; Joined: Sun Mar 29, 2009 6:54 pm; Thanked: 56 times

by ssmiles08 » Sun Jun 07, 2009 5:17 pm

Yes I got (A) too.

It is really asking if x/y is an integer.

3Y^2 + 7Y = X

so Y(3Y+7)/Y = Integer? Yes

Choice 1 works.

choice 2 tells us that (X^2 - X)/Y = integer.

We can't be sure b/c X(X-1) = X^2 - X

either X can be divisible by Y or (X-1) can be divisible by Y or both X and (X-1) are divisible by Y

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houstonrockets16: Junior | Next Rank: 30 Posts; Posts: 26; Joined: Mon Feb 02, 2009 4:45 pm; Thanked: 1 times

by houstonrockets16 » Sun Jun 07, 2009 5:53 pm

A is the answer. Thanks a lot

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