Absolute value

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Source: — Data Sufficiency |

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by pemdas » Wed Feb 29, 2012 5:36 pm
HG10 wrote:Is x = |y - z|?

1. x = y - z
2. y > z

OA: C
prompt: is y-z=x and y-z=-x?
st(1) x=y-z Not Sufficient as we haven't answered on the second question
st(2) y>z implies y-z>0 Not Sufficient as we don't know the sign of x
combining st(1&2): x=y-z and y-z>0 imply x>0 Sufficient

c
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by GMATGuruNY » Wed Feb 29, 2012 7:02 pm
HG10 wrote:Is x = |y - z|?

1. x = y - z
2. y > z

OA: C
Question rephrased: Is x equal to the distance between y and z?
The distance between two values must be positive.

Statement 1: x = y-z.
If y-z>0, then x is equal to the distance between y and z.
If y-z<0, then x is not equal to the distance between y and z.
INSUFFICIENT.

Statement 2: y>z.
No information about x.

Statements 1 and 2 combined:
Since x=y-z and y>z -- implying that y-z>0 -- x is equal to the distance between y and z.
SUFFICIENT.

The correct answer is C.
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by Anurag@Gurome » Wed Feb 29, 2012 9:01 pm
HG10 wrote:Is x = |y - z|?

1. x = y - z
2. y > z

OA: C
(1) x = y - z
If x = 5, y = 10, z = 5, then x = |y - z|
If x = -5, y = 5, z = 10, then x is not equal to |y - z|
No definite answer; NOT sufficient.

(2) y > z or y - z > 0 is NOT sufficient as there is no info about x.

Combining (1) and (2), x = y - z and y - z > 0 implies x > 0. So, x = |y - z| holds true always; SUFFICIENT.

The correct answer is C.
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by Troika » Thu Mar 01, 2012 6:56 am
Thank you for the very helpful explanations!