BTGmoderatorDC wrote:If x + y is not equal to 0. What is the value of (ax + ay)/(x + y)?

(1) x = 4 and y = 5
(2) a = 6

OA B

Source: GMAT Prep

Target question: What is the value of (ax + ay)/(x + y)?
This is a good candidate for rephrasing the target question.

Take the expression: (ax + ay)/(x + y)
Factor the numerator to get: a(x + y)/(x + y)
Simplify the fraction to get: a
Since (ax + ay)/(x + y) = a, we can rephrase the target question...
REPHRASED target question: What is the value of a?

Aside: Here's a video with tips on rephrasing the target question: https://www.gmatprepnow.com/module/gmat- ... cy?id=1100
Now that we've REPHRASED the target question, it should be easy to analyze the two statements.

Statement 1: x = 4 and y = 5
Since we have no information about a, we cannot answer the REPHRASED target question with certainty.
So, statement 1 is NOT SUFFICIENT

Statement 2: a = 6
PERFECT - this is exactly what we need.
Since we can answer the REPHRASED target question with certainty, statement 2 is SUFFICIENT

Answer: B

Cheers,
Brent