X and Y both positive?

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chipbmk
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Topic: X and Y both positive?
PostTue Nov 17, 2009 11:11 pm
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Are x and y both positive?

a. 2x - 2y = 1
b. x⁄y > 1

OA: C

Detailed explanations would be helpful! Thanks Smile
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2010gmat
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PostWed Nov 18, 2009 8:04 am
i have seen a similar question where 1. is 2x - 2y = 1 .... are your sure 1. says 2x.2y = 1???
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sreak1089
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PostWed Nov 18, 2009 8:28 am
I am not able to figure out what a) means in this question.....
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chipbmk
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PostWed Nov 18, 2009 9:32 am
2010gmat wrote:
i have seen a similar question where 1. is 2x - 2y = 1 .... are your sure 1. says 2x.2y = 1???
You are correct, it is 2x-2y = 1 ... I dont know what happened when I copied and pasted it.

Solutions?
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sreak1089
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PostWed Nov 18, 2009 9:52 am
Qn: Are x & y both +ve?

Stmt # 1: 2x - 2y = 1
=> 2(x-y) = 1
=> x-y = 1/2
it means (x-y) > 0
we can further deduce that x > y

This is still NOT SUFFICIENT as x & y can both be +ve or can both be -ve.

Stmt # 2: x/y > 1

Two cases exist: a) x & y both +ve with x > y
b) x & y both -ve with x < y

This is still NOT SUFFICIENT as x & y can both be +ve or both can be -ve.

Combining 1 & 2, we have can only have one case which is x & y both +ve with x > y.
Hence the answer is C
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