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Andrei
- Junior | Next Rank: 30 Posts
- Posts: 28
- Joined: Wed Feb 14, 2007 12:25 am
- Thanked: 1 times
- GMAT Score:690
Hi,
I found the following problem in the Gmatprep test:
Is y < (x+z)/2?
1) y - x < z - y
2) z - y > (z- x)/2
OA is D.
I tried the following way:
1. y - x < z - y => 2y < Z +x => y < (z+x)/2 - SUFFICIENT
2. z - y > (z -x)/2 => 2z - 2y > z -x => z + x > 2y
=> (z+x)/2 > y - SUFFICIENT
So, the answer should be D.
BUT ... the above rationale is correct only if x,y,z are positive, so the signs of the inequalities do not change.
Please help, thanks.
I found the following problem in the Gmatprep test:
Is y < (x+z)/2?
1) y - x < z - y
2) z - y > (z- x)/2
OA is D.
I tried the following way:
1. y - x < z - y => 2y < Z +x => y < (z+x)/2 - SUFFICIENT
2. z - y > (z -x)/2 => 2z - 2y > z -x => z + x > 2y
=> (z+x)/2 > y - SUFFICIENT
So, the answer should be D.
BUT ... the above rationale is correct only if x,y,z are positive, so the signs of the inequalities do not change.
Please help, thanks.
