Inequality problem

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by theCodeToGMAT » Mon Sep 30, 2013 1:10 am
From question:
x = - & y = +
x = + & y = -
So, we need to find whether x & y have opposite signs..

Statement 1: y<x
y & x can have any value
INSUFFICIENT

Statement 2: xy < 0
That means (+) (-) or (-)(+)
SUFFICIENT

Answer [spoiler]{B}[/spoiler]
R A H U L

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by GMATGuruNY » Mon Sep 30, 2013 3:42 am
rakeshd347 wrote:Is |x-y|>|x|-|y| ?

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

OA to follow soon.
|x-y| = the DISTANCE between x and y.

Statement 1: y<x
Case 1: Try to MAXIMIZE the distance between x and y by giving them DIFFERENT SIGNS.
If y=-1 and x=2, then |x-y| = 3 and |x|-|y| = 1.
In this case, |x-y| > |x|-|y|.

Case 2: Try to MINIMIZE the distance between x and y by giving them the SAME SIGN.
If y=1 and x=2, then |x-y| = 1 and |x|-|y| = 1.
In this case, |x-y| = |x|-|y|.

Since in the first case |x-y| > |x|-|y|, and in the second case |x-y| = |x|-|y|, INSUFFICIENT.

Statement 2: xy<0
Case 1 also satisfies statement 2.
In this case, y<x.

Check what happens when xy<0 and x<y.

Case 3: xy<0 and x<y
If x=-1 and y=2, then |x-y| = 3 and |x|-|y| = -1.
As in Case 1, |x-y| > |x|-|y|.

Implication:
If xy<0, then |x-y| > |x|-|y|.
SUFFICIENT.

The correct answer is B.
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