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# What is the value of (1/x − 1/y)? (1) xy/(x − y) = 2 (2) x^2 + y^2 = 5

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Math Expert
Joined: 02 Sep 2009
Posts: 51067
What is the value of (1/x − 1/y)? (1) xy/(x − y) = 2 (2) x^2 + y^2 = 5  [#permalink]

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02 Aug 2018, 00:22
00:00

Difficulty:

15% (low)

Question Stats:

91% (01:18) correct 9% (02:03) wrong based on 35 sessions

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What is the value of (1/x − 1/y)?

(1) xy/(x − y) = 2

(2) x^2 + y^2 = 5

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Joined: 25 Apr 2018
Posts: 351
Re: What is the value of (1/x − 1/y)? (1) xy/(x − y) = 2 (2) x^2 + y^2 = 5  [#permalink]

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02 Aug 2018, 00:29
Bunuel wrote:
What is the value of (1/x − 1/y)?

(1) xy/(x − y) = 2

(2) x^2 + y^2 = 5

if we re-aarange the (1) we get

=>(x-y)/xy=1/2
=>1/y-1/x=1/2
=>1/x-1/y=-1/2
1 is sufficient => A can be our Answer.Strike of B, C and E from the possibilities

Clearly 2 is insufficient itself.
Strike off D

So, IMO A is the Answer.
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Re: What is the value of (1/x − 1/y)? (1) xy/(x − y) = 2 (2) x^2 + y^2 = 5  [#permalink]

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02 Aug 2018, 01:36
= 1/x − 1/y
= (y - x) / xy

(1) xy/(x − y) = 2
Taking the reciprocal and changing the sign of the equation we can find the required value
Sufficient

(2) x^2 + y^2 = 5
Insufficient

Hence, A.
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Re: What is the value of (1/x − 1/y)? (1) xy/(x − y) = 2 (2) x^2 + y^2 = 5 &nbs [#permalink] 02 Aug 2018, 01:36
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