Data Sufficiency

grandh01 wrote:If rs 6= 0 and the points (-r, s) and (s,-r) lie in the same quadrant
of the coordinate plane, is the point (a, b) in this same quadrant?
(1) ab < 0
(2) sb > 0

OA IS A

I imagine where you wrote "rs 6= 0", you mean "rs is not equal to 0".

If we know (-r, s) and (s, -r) are in the same quadrant, then their x-coordinates and y-coordinates have the same sign. So -r and s must have the same sign. Notice that means the points (-r, s) and (s, -r) are either in quadrant I (where everything is positive) or quadrant III (where everything is negative).

If Statement 1 is true, then the coordinates of (a, b) have opposite signs. So (a, b) is in quadrant II or IV, and cannot possibly be in the same quadrant as the points mentioned in the stem. So Statement 1 is sufficient.

Statement 2 tells us that s and b have the same sign, which is helpful, but it gives no information about a, and since we certainly need to know something about the x-coordinate of (a, b), Statement 2 can't possibly be sufficient.

The answer is A.

I'd note, in case some people think they recognize the question, that there's a very similar GMATPrep question with slightly different statements that has a different answer.