Drishti wrote:If a,b,and c are integers, is 2a - b + c greater than a - b - 2c?
(1) a is positive.
(2) c is positive.
Target question: Is 2a - b + c > a - b - 2c?
This is a great candidate for rephrasing the target question.
Aside: We have a free video with tips on rephrasing the target question: https://www.gmatprepnow.com/module/gmat- ... cy?id=1100
Take 2a - b + c > a - b - 2c
Add b to both sides to get: 2a + c > a - 2c
Add 2c to both sides to get: 2a + 3c > a
Subtract a from both sides to get: a + 3c > 0
REPHRASED target question: Is a + 3c > 0?
Statement 1: a is positive.
No information about c, so there's no way to determine whether
a + 3c > 0
Alternatively, we can examine some conflicting cases that satisfy statement 1 (a is positive):
Case a: a = 1 and c = 1, in which case
a + 3c > 0
Case b: a = 1 and c = -1, in which case
a + 3c < 0
Since we cannot answer the
REPHRASED target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: c is positive.
No information about c, so there's no way to determine whether
a + 3c > 0
Alternatively, we can examine some conflicting cases that satisfy statement 2 (c is positive):
Case a: a = 1 and c = 1, in which case
a + 3c > 0
Case b: a = -5 and c = 1, in which case
a + 3c < 0
Since we cannot answer the
REPHRASED target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
Statement 1 tells us that a is positive
Statement 2 tells us that c is positive
If a and c are both positive, then it MUST BE THE CASE that
a + 3c > 0
Since we can answer the
REPHRASED target question with certainty, the combined statements are SUFFICIENT
Answer =
C
Cheers,
Brent
For even more information on rephrasing the target question, you can read this article I wrote for BTG:
https://www.beatthegmat.com/mba/2014/06/ ... t-question
