Is 1/(x-y) < (x-y)? : GMAT Data Sufficiency (DS)
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Is 1/(x-y) < (x-y)?

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Is 1/(x-y) < (x-y)? [#permalink]

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New post 03 Jan 2012, 04:58
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A
B
C
D
E

Difficulty:

  65% (hard)

Question Stats:

50% (02:06) correct 50% (01:31) wrong based on 70 sessions

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Is 1/(x-y) < (x-y)?

(1) x is positive
(2) y is negative
[Reveal] Spoiler: OA

Last edited by Bunuel on 03 Apr 2014, 05:29, edited 2 times in total.
Renamed the topic and edited the question.
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Re: Inequalties [#permalink]

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New post 03 Jan 2012, 05:59
Just look at the question and you will realise that it is only possible if (x-y) is greater than 1. So the question is asking if (x-y) is greater than 1. Now the answer you give "C" is only possible if x and y are integers, which i don't find in the question. For example:

Let x = 0.5
Let y = -0.1

Then (x-y) = 0.6

so 1/(x-y) is greater than than (x-y)

Lets assume, x = 1 and y = -1

than x-y = 2

So 1/(x-y) = 0.5 which satisfies but we don't know if x and y are integers... Did you miss any information in the question while posting. Because the answer to the question you posed is E. If x and y are integers, than the answer is C.
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Re: Inequalties [#permalink]

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New post 03 Jan 2012, 08:53
Nope. I am in the same confusion. Got E too. So was hoping someone could help me out with that.
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Re: Inequalties [#permalink]

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New post 03 Jan 2012, 09:33
Anasthaesium wrote:
Nope. I am in the same confusion. Got E too. So was hoping someone could help me out with that.


I second that. E is the answer.
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Re: Inequalties [#permalink]

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New post 03 Jan 2012, 12:25
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Anasthaesium wrote:
is 1/(x-y) < (x-y)?
1) x is positive
2) y is negative


+1 E

Combining (1) and (2), let's pick numbers:

a) \(x=2 , y= -1\), then \(\frac{1}{(2+1)} < (2+1)\)

b) \(x=0.25 , y= -0.25\), then \(\frac{1}{(0.50)} > (0.50)\). Simplifying \(2 > 0.5\)

INSUFFICIENT
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Re: Inequalties [#permalink]

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New post 03 Jan 2012, 13:19
Absolutely, E. Took 2.5 minutes to solve though. Number plugging is the key.

1. x +ve -> integers [4-2]>1/[4-2], but (3-2) = 1/(3-2) Insufficient
2. y -ve -> integers [2-(-1)]>1/[2-(-1)], but [0-(-1)] = 1/[0-(-1)]

Now, it gets tricky. Together, use both integers and fractions
[2-(-1)]>1/[2-(-1)]. However, [0.3-(-0.2)]<1/[0.3-(-0.2)]

TAKEAWAY: Start by proving insufficiency with integers only first, then move to fractions/Zero plugging if need be.

The OA here is incorrect.
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Re: Is 1/(x-y) < (x-y)? [#permalink]

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New post 03 Apr 2014, 04:42
Anasthaesium wrote:
Is 1/(x-y) < (x-y)?

(1) x is positive
(2) y is negative


Getting E too
Yes OA seems incorrect.Can Moderator Please change the OA or provide explanation for C. Thank you.
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Re: Is 1/(x-y) < (x-y)? [#permalink]

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New post 09 Aug 2016, 09:10
It is clear that both statements are insufficient since we don't know anything about either x or y

Now from 1+2 we know that (x-y) is positive. And hence we can multiply both sides by (x-y) Hence we have (x-y)^2>1 If x and y are integeres then the answer is Yes. But if x and y are fractions then answer will be No. Hence E
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Re: Is 1/(x-y) < (x-y)?   [#permalink] 09 Aug 2016, 09:10
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