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If 1/x + 1/y = 1/3, then xy/(x + y) =

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Math Expert
Joined: 02 Sep 2009
Posts: 58312
If 1/x + 1/y = 1/3, then xy/(x + y) =  [#permalink]

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10 Apr 2019, 23:18
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Difficulty:

25% (medium)

Question Stats:

73% (00:30) correct 27% (00:24) wrong based on 11 sessions

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If $$\frac{1}{x} + \frac{1}{y} = \frac{1}{3}$$, then $$\frac{xy}{x + y} =$$

(A) 1/5
(B) 1/3
(C) 1
(D) 3
(E) 5

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Joined: 01 May 2017
Posts: 82
Location: India
Re: If 1/x + 1/y = 1/3, then xy/(x + y) =  [#permalink]

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11 Apr 2019, 00:10
If $$1/x+1/y=1/3$$ , then $$xy /x+y$$=

(A) 1/5
(B) 1/3
(C) 1
(D) 3
(E) 5

$$1/x+1/y=1/3$$ = $$x+y/ x*y$$ = 1/3
implies $$x*y/x+y$$ = 3

Option D is correct
Re: If 1/x + 1/y = 1/3, then xy/(x + y) =   [#permalink] 11 Apr 2019, 00:10
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