Data Sufficiency

lheiannie07 wrote:Is kw>0?

(1) k - w = 10

(2) k^2 = w^2

Which of the statement is sufficient?

OA C

kw > 0 if k and w are each positive or each negative.

(1) k - w = 10

Case 1: Say k is positive = 8 and w is negative = -2, the answer is No.
Case 2: Say k is positive = 12 and w is positive = 2, the answer is Yes.

No unique answer. Insufficient

(2) k^2 = w^2

=> k = ±w

Case 1: If k = w, then kw > 0, the answer is Yes.
Case 2: If k = -w, then kw < 0, the answer is No.

No unique answer. Insufficient

(1) and (2) together

k - w = 10 and k = ±w are comparible only if k = -w.

=> -w -w = 10 => w = -5 and k = 5, thus kw = 5*-5 = -10 < 0, the answer is No. Sufficient.

The correct answer: C

Hope this helps!

-Jay
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