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multiple question

by lachlanc » Mon Nov 17, 2008 6:53 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

OA: A
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Source: — Data Sufficiency |
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Re: multiple question

by logitech » Mon Nov 17, 2008 7:04 pm
lachlanc 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

OA: A
1) y(3y+7) = X

X is a multiple of Y, for every Y there is a y (3y+7) X

SUF

2) x( x-1) = Y ( integer )

Either X or (x-1) is a multiple of Y but we don't know

INSUF

Hence, A
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by cramya » Mon Nov 17, 2008 7:13 pm
Stmt I

3 y ^2 + 7y = x

y (3y+7) = x

For X to be a multiple of Y
y * some integer shoulld equal x

Here we have y * (3y+7) = x (3y+7 is always an integer sinc eits product of 2 intgers + an integer)

SUFF

Stmt II

y * k = x ( x-1)


Either x is a mutiple of of y or x-1 is a mutiple of of y dont know

INSUFF

Eg:

2*3 = 3*2 (y=2 k=3 x=3 x-1=2 here x-1 mutiple of y)
3*10 = 6*5 (y=3 k=10 x=6 x-1=5 here x is a mutiple of y)
A)
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