Data Sufficiency

jjjinapinch wrote:Is rw = 0?
(1) −6 < r < 5
(2) 6 < w < 10

Official Guide question
Answer: E

Target question: Is rw = 0?
Since each statement ALONE fails to provide information about both variables, let's jump straight to....

Statements 1 and 2 combined
There are several values of r and w that BOTH statements. Here are two:
Case a: r = 0 and w = 7, in which case rw = (0)(7) = 0
Case b: r = 1 and w = 7, in which case rw = (1)(7) = 7
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer: E

Cheers,
Brent

jjjinapinch wrote:Is rw = 0?
(1) −6 < r < 5
(2) 6 < w < 10

Official Guide question
Answer: E

We have to see whether rw = 0?

rw = 0 if at least of the two variables r and w is 0, else not.

Statement 1: −6 < r < 5

From this inequality, we get that r may or may not be 0.

If r = 0, rw = 0, the answer is YES.
However, if r ≠ 0, then we do not have any information about w. If w ≠ 0, then rw ≠ 0, thus, the answer is No. Insufficient.

Statement 2: 6 < w < 10

From this inequality, we get that w ≠ 0. But we do not know about r. It may or may not be 0. Insufficnet.

Statement 1 & 2:

Even after combining the two statements, we cannot get the unique answer as r may or may not be 0, making rw may or may not be 0. Insufficient.

The correct answer: E

Hope this helps!

Download free ebook: Manhattan Review GMAT Quantitative Question Bank Guide

-Jay
_________________
Manhattan Review GMAT Prep

Locations: New York | Bangkok | Abu Dhabi | Rome | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.

Hi All,

We're asked if (R)(W) = 0. This is a YES/NO question and can be solved by TESTing VALUES. This question serves as an example of how thinking about the specific question that is asked can help you to quickly work through the information in the two Facts. For (R)(W) to equal 0, at least one of the two variables would have to equal 0. If neither of the variables equals 0, then the answer to the question is NO.

1) -6 < R < 5

IF....
R=0 and W=7, then the answer to the question is YES
R=1 and W=8, then the answer to the question is NO
Fact 1 is INSUFFICIENT

2) 6 < W < 10

IF....
R=0 and W=7, then the answer to the question is YES
R=1 and W=8, then the answer to the question is NO
Fact 2 is INSUFFICIENT

Combined, we already have two TESTs that 'fit' both Facts and lead to different answers (one "YES" and one "NO")
Combined, INSUFFICIENT

Final Answer: E

GMAT assassins aren't born, they're made,
Rich