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arjtryarjtry
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Is X^2 * Y^5 * Z > 0 ? 1. \frac{XZ}{Y} > 0 2. 01 Sep 2008, 04:29
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Is \(X^2 * Y^5 * Z > 0\) ?

1. \(\frac{XZ}{Y} > 0\)
2. \(\frac{Y}{Z} < 0\)



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Is X^2 * Y^5 * Z > 0 ? 1. \frac{XZ}{Y} > 0 2. 01 Sep 2008, 06:13
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The answer should be C.

(1) if y is negative, then either X or Z must be negative. So if y is negative and Z is negative, then the overall product will be positive. However, if Y is negative and X is negative, then the overall product will be negative because y^5 will be negative and any positive number multiplied by a negative will always be negative.

(2) No information about X. for all we know, X could be a zero.

(1&2) So we know that X is not a zero. But when you consider the different scenarios, the product will always be negative since X^2 will always be positive. So when either X or Z has to be a negative, the overall product will always be negative. We know this because their powers are odd and so it will maintain their original signs.
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Is X^2 * Y^5 * Z > 0 ? 1. \frac{XZ}{Y} > 0 2. 01 Sep 2008, 14:36
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arjtryarjtry
Is \(X^2 * Y^5 * Z > 0\) ?

1. \(\frac{XZ}{Y} > 0\)
2. \(\frac{Y}{Z} < 0\)
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X^2 * Y^5 * Z >0 --> X^2 * Y^4* YZ>0
--> YZ>0

1) XZ/Y >0

Not suffcieint Z/Y can be -ve or +ve based on X

2) Y/Z<0 means Y and Z must have opposite signs

YZ<0

X^2 * Y^4* YZ>0 is not true

even if X=0 X^2 * Y^4* YZ>0 is not true

So we don't require X value.

I will go with B.

What is OA.
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Is X^2 * Y^5 * Z > 0 ? 1. \frac{XZ}{Y} > 0 2. 01 Sep 2008, 15:05
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C

B is not suff because x can be 0, which make the equation \(X^2 * Y^5 * Z = 0\)
if x is not 0, then y and z would come into play.
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Is X^2 * Y^5 * Z > 0 ? 1. \frac{XZ}{Y} > 0 2. 01 Sep 2008, 15:44
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arjtryarjtry
Is \(X^2 * Y^5 * Z > 0\) ?

1. \(\frac{XZ}{Y} > 0\)
2. \(\frac{Y}{Z} < 0\)
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C

Here, you need to know whether Y and Z are the same sign and that none of the values are 0.

(1) Insufficient

Tells you that none of the variables are 0 and that XZ and Y are the same sign.

(2) Insufficient

Tells you that Y and Z are the same sign.

(1) and (2) Sufficient
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Is X^2 * Y^5 * Z > 0 ? 1. \frac{XZ}{Y} > 0 2. 01 Sep 2008, 15:55
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gmatnub
C

B is not suff because x can be 0, which make the equation \(X^2 * Y^5 * Z = 0\)
if x is not 0, then y and z would come into play.
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Question is X^2 * Y^5 * Z > 0
when x=0 :X^2 * Y^5 * Z = 0 -- Answer to the question is "NO"
when x<>0 : X^2 * Y^5 * Z < 0 --> Answer to the question is "NO"

Suffcient
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Is X^2 * Y^5 * Z > 0 ? 1. \frac{XZ}{Y} > 0 2. 01 Sep 2008, 16:39
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x2suresh
gmatnub
C

B is not suff because x can be 0, which make the equation \(X^2 * Y^5 * Z = 0\)
if x is not 0, then y and z would come into play.


Question is X^2 * Y^5 * Z > 0
when x=0 :X^2 * Y^5 * Z = 0 -- Answer to the question is "NO"
when x0 : X^2 * Y^5 * Z Answer to the question is "NO"

Suffcient
Show more


hmmm...good point actually because whether X is zero or not, the result will still not be positive. good catch. so i guess the answer is B



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