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Absolution

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Source: — Data Sufficiency |

by neelgandham » Fri Oct 21, 2011 3:18 am
If x, y, and z are nonzero numbers, is (x)(y + z) > 0?

Implies is x>0 if (y+z)>0 ? or Is x<0 if (y+z)<0 ?

(1) |x + y| = |x| + |y|

Implies x > 0 and y > 0 or x < 0 and y < 0 - Insufficient as it doesn't speak of z

(2) |z + y| = |y| + |z|

Implies z > 0 and y > 0 or z < 0 and y < 0 - Insufficient as it doesn't speak of x

From 1 and 2

Take condition x > 0 and y > 0, then the value of z > 0 [spoiler]and (x)(y + z) > 0[/spoiler]
Take condition x < 0 and y < 0, then the value of z < 0 [spoiler]and (x)(y + z) > 0[/spoiler]

Hence option C
Anil Gandham
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by bpdulog » Fri Oct 21, 2011 7:31 am
C based on same rationale as above.
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by tpr-becky » Fri Oct 21, 2011 8:42 am
This is about the concept of positive, negative, zero.

for the question to be always true both x and (y+z) must either both be positive or both be negative.

Statement 1 - tells us that both x and y are the same sign but no info about z so insufficient and BCE.

Statement 2 - tells us that both y and z are the same sign but no info about x so insufficient and CE.

If you put them together you find that all three are the same sign - if they are all positive then the multiplication will be positive. if they are all negative then you will have a neg(neg) which is positive.

Therefore C is enough to solve the problem.
Becky
Master GMAT Instructor
The Princeton Review
Irvine, CA
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