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# Data Sufficiency

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Manager
Joined: 21 Feb 2009
Posts: 104

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14 Mar 2009, 16:34
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Data Sufficiency
Are x and y both positive?
1. 2x-2y=1
2. x/y > 1
Director
Joined: 01 Apr 2008
Posts: 847
Name: Ronak Amin
Schools: IIM Lucknow (IPMX) - Class of 2014

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15 Mar 2009, 03:17
Should be E. wat is OA?

From 1) , 2(x-y) = 1 => x-y = 1/2 => x and y have the same sign.

From 2) x and y have the same sign.

Combined, we can be sure that x and y are both positive or negative.
Manager
Joined: 21 Feb 2009
Posts: 104

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15 Mar 2009, 03:40
From 1) , 2(x-y) = 1 => x-y = 1/2 => x and y have the same sign.

From this how did you come to conclusion that x and y have same sign??

This question is from GMATPrep.I also marked E but correct answer is C (Both statements together are sufficient)
Director
Joined: 01 Apr 2008
Posts: 847
Name: Ronak Amin
Schools: IIM Lucknow (IPMX) - Class of 2014

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15 Mar 2009, 04:43
sorry dude..i plugged in some wrong numbers..yes we cant say anything from x-y = 1/2..
I have the following explanation for C..
1) x-y=1/2
2) x/y >1 => x and y have same sign and magnitude of x is greater than magnitude of y ( for x/y to be greater than 1)

So, if we consider both x and y to be positive then,
some positive - some positive = 1/2 ( some positive) => possible

if we consider both x and y to be negative then,
(negative with higher magnitude) - (negative with lower magnitude) cannot give a positive number (1/2)... eg. -6 - (-3) will always give a negative number

hence, both when we take 1 and 2, x and y both should be positive...

What is OE?
nitindas wrote:
From 1) , 2(x-y) = 1 => x-y = 1/2 => x and y have the same sign.

From this how did you come to conclusion that x and y have same sign??

This question is from GMATPrep.I also marked E but correct answer is C (Both statements together are sufficient)
Manager
Joined: 02 Mar 2009
Posts: 129

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15 Mar 2009, 06:01
Yes..

That is the right explanation Economist. C it is.
SVP
Joined: 07 Nov 2007
Posts: 1761
Location: New York

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15 Mar 2009, 07:03
1
KUDOS
nitindas wrote:
Data Sufficiency
Are x and y both positive?
1. 2x-2y=1
2. x/y > 1

1. X,Y both can be positive
or x is +ve y is -ve

not sufficient
2)
x,y both must be +ve or -ve
not sufficient

combined

2x-2y=1 --> x/y -1= 1/2y

1/2y = x/y-1 = +ve (since x/y >1 )

so y +ve .. obvisouly x must be +Ve

C.
_________________

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Manager
Joined: 21 Feb 2009
Posts: 104

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15 Mar 2009, 12:21
great explanation..!!
Re: Data Sufficiency   [#permalink] 15 Mar 2009, 12:21
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# Data Sufficiency

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