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Is x-y+1 greater than x+y-1 ?

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Source: — Data Sufficiency |

Re: Is x-y+1 greater than x+y-1 ?

by Brent@GMATPrepNow » Thu Aug 20, 2020 7:56 am
BTGModeratorVI wrote:
Thu Aug 20, 2020 7:20 am
Is x-y+1 greater than x+y-1 ?

(1) x > 0
(2) y < 0

Answer: B
Source: GMAT prep
Target question: Is x - y + 1 > x + y - 1 ?
This is a good candidate for rephrasing the target question.

Take: x - y + 1 > x + y - 1
Subtract x from both sides to get: -y + 1 > y - 1
Add y to both sides to get: 1 > 2y - 1
Add 1 to both sides to get: 2 > 2y
Divide both sides by 2 to get: 1 > y
REPHRASED target question: Is y < 1?

The video below has tips on rephrasing the target question

Statement 1: x > 0
Since we have no information about y, we cannot answer the REPHRASED target question with certainty
Statement 1 is NOT SUFFICIENT

Statement 2: y < 0
In other words, y is NEGATIVE
If is NEGATIVE, then y is definitely less than 1
So, the answer to the REPHRASED target question is YES, y IS less than 1
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer: B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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