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Is x + y positive ?

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Source: — Data Sufficiency |
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by lkm » Tue Apr 06, 2010 5:31 am
rockeyb wrote:
Is x + y positive ?

(1) x- y is positive .

(2) y - x is negative .
IMO (E).

Question can be rephrased as is x + y > 0

With statement (1),

x - y > 0

i.e. x > y

if both x and y are positive then

is x + y > 0
YES

but if both x and y are negative (example, x = -2 and y = -3) then

is x + y > 0
NO

Since you get YES and NO for the 1st statement, hence INSUFFICIENT


Statement 2 is nothing but rephrased of statement (1).

i.e

y - x < 0
y < x
x > y

Hence, statement (2) is also INSUFFICIENT

Together also both statements are INSUFFICIENT

Choose (E)
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by eaakbari » Tue Apr 06, 2010 6:27 am
IMO C

But my method of picking numbers took a little long, does anyone have any inputs?

Do give OA
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by ajith » Tue Apr 06, 2010 6:44 am
rockeyb wrote:Is x + y positive ?

(1) x- y is positive .

(2) y - x is negative .
1) and 2) reveal the same information

if x-y >0
y-x <0

so it is either D or E

now say x =3 and y = -4

x-y>0 and x+y <0

consider x= 3 and y = -1

x-y>0 and x+y >0
[spoiler]
So E[/spoiler]
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by rockeyb » Tue Apr 06, 2010 7:59 am
@ajith ,

excellent explanation

x+y = -(y - x )

so statements 1 and 2 in fact give the same information.

OA E
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by tata » Tue Apr 06, 2010 11:18 am
rockeyb wrote:Is x + y positive ?

(1) x- y is positive .

(2) y - x is negative .
Is it possible that both the statements in a DS question give the same information?
I have seen scenarios where a statement rephrases the information given in question but can 1 and 2 say the same thing on GMAT?
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by Stuart@KaplanGMAT » Tue Apr 06, 2010 12:23 pm
tata wrote:
rockeyb wrote:Is x + y positive ?

(1) x- y is positive .

(2) y - x is negative .
Is it possible that both the statements in a DS question give the same information?
I have seen scenarios where a statement rephrases the information given in question but can 1 and 2 say the same thing on GMAT?
This definitely happens on the real GMAT.

Further, when you see that the two statements are identical, you can automatically eliminate A, B and C, even if you don't understand the question.
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