X, Y & Zero

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Source: — Data Sufficiency |

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Re: X, Y & Zero

by Ian Stewart » Sun Aug 17, 2008 7:01 am
smclean23 wrote:If xy &#8800; 0, is x/y<0 ?
(1) x = y
(2) –x = - ( - y )



Answer is D.
Where is the question from? It is not a well-designed GMAT question; the two statements contradict each other, which is not permitted on the real test.

We know x and y are not both zero. The question asks, 'is x/y < 0?', which is the same as asking 'do x and y have opposite signs?'.

From 1), if x and y are equal, they have the same sign, so the answer to the question is definitely 'no'. Sufficient.

From 2), we have -x = y, so x and y have opposite signs. The answer to the question is definitely 'yes'. Sufficient.

But it's not a real GMAT question.
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