Data Sufficiency

BTGModeratorVI wrote: ↑

Mon Jul 13, 2020 7:53 am

Is k positive?

(1) k + 1 < 1 − k
(2) 1/k < 0

Answer: D
Source: Economis GMAT

Target question: Is k positive?

Statement 1: k + 1 < 1 − k
Add k to both sides of the inequality to get: 2k + 1 < 1
Subtract 1 from both sides of the inequality to get: 2k < 0
Divide both sides by 2 to get: k < 0 (in other words, k is negative)
The answer to the target question is NO, k is definitely not positive
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: 1/k < 0
Since 1 is POSITIVE, this statement is telling us that: POSITIVE/k = NEGATIVE
This means k must be negative.
The answer to the target question is NO, k is definitely not positive
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: D

Cheers,
Brent