Inequalities

[BTGmoderatorRO]

Is m not equal to n ?
(1) m + n < 0
(2) mn < 0
How will i know the correct statement here?

[Jay@ManhattanReview]

Is m not equal to n ?

(1) m + n < 0
(2) mn < 0

How will i know the correct statement here?

(1) m + n < 0

Case 1: If, for example, m = n = -2, then m + n = -4 < 0. The answer is No.
Case 2: If, for example, m = -2 and n = -1, then m + n = -3 < 0. The answer is Yes. Insufficient

(2) mn < 0

=> Since m.n < 0, implying negative, one of m and n is positive and the other is negative. This implies that m not equal to n. Sufficient.

The correct answer: B

Hope this helps!

-Jay

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