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Source: — Data Sufficiency |

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by Rahul@gurome » Sat Oct 30, 2010 3:24 am
sindhujah_kk wrote:Is |x| = y-z?

1) x+y = z

2) x<0

Ans: C
Please explain.
Statement 1: x + y = z.
Thus, x = z - y. Now,
  • (1) |x| = x = z - y ; If x is positive
    (2) |x| = -x = y - z ; If x is negative
Not sufficient.

Statement 2: x < 0. No information about y and z.

Not sufficient.

1 & 2 Together: x is negative. Therefore, |x| = -x = y - z.

Sufficient.

The correct answer is C.
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by limestone » Sat Oct 30, 2010 3:27 am
Hi,

|x| = x if x>0,

|x| = -x if x<0

1. x + y = z means
x = z - y, then
If x > 0, |x| = |z - y| = z-y
If x<0, |x| = |z-y| = -(z-y) = y - z
Thus 1 is insuff.

2. x<0, and there is no other relationship among x,y,z. Hence, 2 is clearly insufficient.

1&2.
x + y = z <=> x = z - y
As x<0, |x| = |z -y| = -(z-y) = y - z ( as z - y = x <0)
Thus 1&2 is suff.

Pick C.
"There is nothing either good or bad - but thinking makes it so" - Shakespeare.
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