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Source: — Data Sufficiency |
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Re: Gmat Prep

by maihuna » Mon Oct 26, 2009 9:48 am
John Corn wrote:x not equal to -y

is (x-y)/(x+y)>1?

1) x>0
2) y<0

Please help [/u]
x-y
---- -1 > 0
x+y

x-y-x-y
-------- >0
x+y

y/(x+y) < 0

If x>0 we do not know anything about y insuff
If y<0 we do not know anything abt x insuff

If x>0 and y<0 depends on its value for the sign of x+y, not since y<0 the sum y/(x+y) < 0 means 1/(x+y) > 0 but that is not always true, if y=-2 x =1 we have x+y = -1 while y=-2 x=3 means x+y =1

so E.
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by John Corn » Mon Oct 26, 2009 10:30 am
Thanks maihuna for your response.
I have a question

Why can't you solve it with this equality
(x-y)>(x+y)?

With this I am getting that B is sufficient.

Thanks in advance.
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by xcusemeplz2009 » Mon Oct 26, 2009 12:18 pm
John Corn wrote:Thanks maihuna for your response.
I have a question

Why can't you solve it with this equality
(x-y)>(x+y)?

With this I am getting that B is sufficient.

Thanks in advance.
in inequalities dividing or multipying any unknown variable(+or-ve) always leads to two outcomes a positive or a negative

since x-y is + or -ve it is unknown cross multiplying may or may not req change of sign....

therefore whn sign is unknown its always better to limit the operation upto addition or sub...

HTH
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by John Corn » Mon Oct 26, 2009 1:39 pm
Thanks so much.
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Re: Gmat Prep

by life is a test » Wed Oct 28, 2009 8:12 am
maihuna wrote: x-y-x-y
-------- >0
x+y

y/(x+y) < 0
maihuna - is the second formula supposed to read 2y/x+y?

I dont think it makes a difference to the ans but just wanted to check i was reducing it correctly when i worked it out.

thks
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Quick Question

by chris6 » Fri Oct 30, 2009 9:21 am
x-y
---- -1 > 0
x+y

How did you get -x-y in the numerator from -1?

x-y-x-y
-------- >0
x+y
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i have a question!

by khushboo143 » Sun Nov 01, 2009 3:25 pm
x-y
---- -1 > 0
x+y

x-y-x-y
-------- >0
x+y

till here i got it but then hoe did u got the below step..

y/(x+y) < 0

i got stucked at
-2y
---- > 0
x+y

pls help!!!
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