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# Is xy>0? 1) x-y>-2 2) x-2y<-6 OA is C. Can anyone

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Is xy>0? 1) x-y>-2 2) x-2y<-6 OA is C. Can anyone [#permalink]

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15 Jan 2009, 20:56
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Is xy>0?

1) x-y>-2
2) x-2y<-6

OA is C. Can anyone explain why?

Kudos [?]: 3 [0], given: 0

Intern
Joined: 05 Jan 2009
Posts: 9

Kudos [?]: 5 [0], given: 0

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16 Jan 2009, 01:33
I think it is quite obvious that a and b are not suff but themselves (you can find plenty of cases to see it). So let's joint the 2 inequalities and see what happen:

x-y>-2
x-2y<-6
This is the same as:
x-y>-2
-x+2y>6
The result of combining both is: y>4
We can use the first inequality now: x-4>-2; x>2
So the answer is C because we know that combining both ineq. y>4 and x>2 so xy>0

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Intern
Joined: 16 Jan 2009
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16 Jan 2009, 17:43
Is xy>0?

1) x-y>-2
2) x-2y<-6

OA is C. Can anyone explain why?

Its a yes/no question.
xy>0 implies that xy is positive which means either x and y both should be positive or x and y both should be negative.

statement1. x - y > - 2 or x > y - 2
if y = -1 then x could be -2 which gives yes
if y = -1 then x could be 3 which gives No
so statement 1 is insufficient

statement2. similarly statement2 is also insufficient.

Taking together

two inequalities ....add them ( change the inequality of the second statement to - x + 2y > 6) we get

y > 4 ( so y is positive)

now in statement1 if y > 4 then x > 2 ....so Yes xy > 0 since x and y both positive
in statement 2 if y > 4 then x > 2 ... so Yes xy> 0 .

so the answer is C .

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Re: DS- Number property   [#permalink] 16 Jan 2009, 17:43
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