Gmat prep

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Source: — Data Sufficiency |

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by liferocks » Tue Apr 27, 2010 4:56 am
from 1 x=y(3y+7)..x is multiple of y as 3y+7 is integer-- sufficient
from 2 x(x-1)=y ..not sufficient
ans A

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by iamseer » Tue Apr 27, 2010 5:03 am
x>0, y>0
From 1:
y(3y+7)=x
since y is an integer greater than 0, (3y+7) is an integer. Therefore x is (3y+7)th multiple of y
SUFFICIENT

From 2:
x(x-1)=yn where n is an integer.

let x=3
x(x-1)=6

If y = 2, n=3 x is not a multiple of y
If y = 3, n=2 x is a multiple of y
NOT SUFFICIENT

answer A
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