baladon99 wrote:Is |X-Y| > |X| -|Y| ?
1) Y < X
2) XY< 0
This is a GMAT prep problem.
(1) If Y = 3, X = 4, then |X - Y| = |4 - 3| = 1 and |X| - |Y| = 4 - 3 = 1. Here, |X - Y| = |X| - |Y|
If Y = -4, X = -3, then |X - Y| = |-3 - (-4)| = 1 and |X| - |Y| = 3 - 4 = -1. Here, |X - Y| > |X| - |Y|
No definite answer.
So, (1) is NOT SUFFICIENT.
(2) For XY < 0, either X should be positive, Y should be negative, or X should be negative, Y should be positive.
Generally, it can observed that |X - Y| will be the sum of X and Y, as one of them is negative and other is positive, while |X| - |Y| will be the difference in X and Y, which will obviously be less than |X - Y|. See the examples below:
If X = -3, Y = 4, then |X - Y| = |-3 - 4| = 7 and |X| - |Y| = 3 - 4 = -1. Here, |X - Y| > |X| - |Y|
If X = 8, Y = -4, then |X - Y| = |8 + 4| = 12 and |X| - |Y| = 8 - 4 = 4. Here, |X - Y| > |X| - |Y|
So, (2) is SUFFICIENT.
The correct answer is B.