Gmat Prep - Divisibility

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Gmat Prep - Divisibility

by mttorii » Mon Jul 09, 2007 12:01 pm
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

Appreciate any help I can get.

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Re: Gmat Prep - Divisibility

by gabriel » Mon Jul 09, 2007 12:29 pm
mttorii wrote: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

Appreciate any help I can get.


for x to be a multiple of y we need y*a=x ..where a is a integer ..

from the first statement we get y(3y+7)=x ..where 3y+7 will be an inetger so from this we get x is a multiple of y .. so statement one is sufficient ..

from the second statement we have x(x-1)= y*a .. wherea is an integer ..

now let us investigate further .. suppose x = 2 then x(x-1)=2 so y =2 in which case x is a multiple of y

.. suppose x = 3 then x(x-1) = 6 .. in which case y can take values of 2,3,6 .. if y is 2 then x is not a multiple of y .. but if y is 3 then x is a multiple of y .. so we dont get a defnite answer from statemen 2 so the statement is insufficient .. so the answer is A ...