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Positive/Negative Number properties

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by 2008 » Wed Aug 06, 2008 1:46 pm
9x=4y is sufficient to answer, hence either A or D

x>-y is not sufficient, hence A.
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by kshin78 » Wed Aug 06, 2008 1:55 pm
2008 wrote:9x=4y is sufficient to answer, hence either A or D

x>-y is not sufficient, hence A.
Wouldn't it be E because:

9x = 4y ----> x = (4/9)y

here when x = -4/9 y= -1 x> y

when x = 4/9 y=1 x<y

therefore A is not sufficient.

B is also not sufficient

Thus, E.

What's the oA?
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by parallel_chase » Wed Aug 06, 2008 2:07 pm
The answer should be E.

Statement I

9x=4y
x=4
y=9
36=36, x<y

x=-4
y=-9
-36 = -36, x>y

Hence Insufficient.

Statement II

x>-y

It does not tell us anything about positive y, therefore insufficient.


Hence the answer is E.

Whats the OA?
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by jessicamuniz » Wed Aug 06, 2008 3:26 pm
Hi guys it is me again.
Thanks for all the answers and I also agree with you and I say that the answer is letter E.
However, this problem comes form the GMAT Kaplan book and in the answers it actually said that the right answer is letter C.
I read the explainations already but I still do not get it.
What do you think about this ???
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by arorag » Wed Aug 06, 2008 4:45 pm
parallel_chase wrote:The answer should be E.

Statement I

9x=4y
x=4
y=9
36=36, x<y

x=-4
y=-9
-36 = -36, x>y
SEE the second condition

Hence Insufficient.

Statement II

x>-y

It does not tell us anything about positive y, therefore insufficient.


Hence the answer is E.

It should be C. See second condition

Whats the OA?
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by kris610 » Thu Aug 07, 2008 11:34 am
I agree with C.

First says, both x and y could be 0, in which case it is a NO. For +ve y, x <y and -ve y, x > y.

Second statement by itself is not sufficient.

Now, from (1), we have x = (4/9) y. From 2, we have (x+y) > 0. Put these together, and you get y>0, in which case x<y.
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by BlueRain » Thu Aug 07, 2008 11:44 am
We can all agree that neither statements is sufficient alone, thus it comes down to C or E.

9x = 4y
x > -y

multiple the second equation by 9
9x > -9y
4y > -9y (substitute 9x with 4y according to 1st equation)
y > 0
x > 0 (x = 4/9y and y>0)
if they are both positive, x = 4/9y must be x < y.

C. Hope this helps.
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