BTGModeratorVI wrote: ↑Fri May 29, 2020 6:32 am
If x > y, is cx > cy ?
(1) c > 0
(2) xy > 0
Answer:
A
Source: GMAT prep
Given: x > y
If we subtract y from both sides of the inequality, we get x - y > 0
In other words,
x - y is positive
Target question: Is cx > cy ?
This is a good candidate for
rephrasing the target question.
Take:
Is cx > cy ?
Subtract cy from both sides to get:
Is cx - cy > 0 ?
Factor to get:
Is c(x - y) > 0 ?
Since we already know that
x - y is positive, we get:
Is c(some positive number) > 0 ?
In order for c(some positive number) to be positive,
c must be positive
So the target question is really asking us whether c is positive
REPHRASED target question: Is c > 0 ?
Aside: Here’s a video with tips on rephrasing the target question: https://www.gmatprepnow.com/module/gmat- ... cy?id=1100
Statement 1: c > 0
Perfect!!
The answer to the REPHRASED target question is
YES, c is positive
Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: xy > 0
Since statement 2 provides no information how about the value of c, there's no way to answer the
REPHRASED target question with certainty
Statement 2 is NOT SUFFICIENT
Answer: A
Cheers,
Brent
