Data Sufficiency

sam2304 wrote:How can you come up with the value of x using statement 2 ? Or am i missing something here ?

is xy = -1 ?

we cannot substitute y = 1 in xy = -1 and say x = -1. xy can be = 4 or 8 or -12. You can substitute only if it is given as 'if xy = -1'.

A.x = y => is xy = -1 ? No. SUFF.
B.y = 1 => is xy = -1 ? We don't have value of x so INSUFF.

IMO A.

Hope i am right

Anurag@Gurome wrote:

Strongt wrote:is xy = -1?

1) x=y
2) y=1

Answer is A

and I understand why, but looking at statement 2, I can come up with a value for x

(1) x = y implies that xy cannot be equal to -1, because for their product to be -1, one of them should be positive and other should be negative, which cannot be the case as x = y. So, statement 1 is sufficient to answer the question asked.

(2)y = 1 implies x * (1) = -1, which implies x = -1. So xy = -1, which is again sufficient to answer the given question.

But there is a contradiction in this question, 1st statement says x = y and the 2nd one says x is not equal to y, so the answer to the main question changes. But this cannot be the case in a good GMAT question.