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# If x#-y, is x-y/x+y > 1? 1.) x > 0 2.) y < 0 These

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Manager
Joined: 17 Dec 2008
Posts: 176
Followers: 2

Kudos [?]: 142 [0], given: 0

If x#-y, is x-y/x+y > 1? 1.) x > 0 2.) y < 0 These [#permalink]

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02 Mar 2009, 18:51
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0% (00:00) correct 100% (00:04) wrong based on 1 sessions

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If x#-y, is x-y/x+y > 1?

1.) x > 0
2.) y < 0

These problems always get me, I tend to pick one as 0, what is correct approach?
Pick numbers and prove 2 answers Y/N?
Manager
Joined: 26 Dec 2008
Posts: 58
Schools: Booth (Admit R1), Sloan (Ding R1), Tuck (R1)
Followers: 2

Kudos [?]: 13 [0], given: 0

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02 Mar 2009, 19:54
ConkergMat wrote:
If x#-y, is x-y/x+y > 1?

1.) x > 0
2.) y < 0

These problems always get me, I tend to pick one as 0, what is correct approach?
Pick numbers and prove 2 answers Y/N?

for f = (x-y)/(x+y) > 1 to be true:

(I) x - y and x + y need to have same sign
(II) abs. value of (x - y) needs to be greater than abs value of (x + y)

(1) x > 0

for y>0 f < 1

for certain value of y < 0 (where |y| < |x|) f > 1

=> A insufficient --> D insufficient

(2) similar argument for y < 0 --> B insufficient

with (1)&(2) combined:

f > 1 if x > |y|
f < 1 if x < |y|

=> C insufficient

Re: DS: Number properties   [#permalink] 02 Mar 2009, 19:54
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