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If the operation x&y is defined by the equation x&y=x·y/(x+y) for all

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If the operation x&y is defined by the equation x&y=x·y/(x+y) for all [#permalink]

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New post 21 Mar 2017, 09:18
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A
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C
D
E

Difficulty:

  5% (low)

Question Stats:

93% (00:43) correct 7% (01:24) wrong based on 71 sessions

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Re: If the operation x&y is defined by the equation x&y=x·y/(x+y) for all [#permalink]

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New post 21 Mar 2017, 11:13
Bunuel wrote:
If the operation x&y is defined by the equation x&y=x·y/(x+y) for all x≠−y, then (18)&(9)=

A. 2
B. 3
C. 6
D. 9
E. 12


(18)&(9) = 18*9/(18+9) = 18*9/27 = 6

Answer - C
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If the operation x&y is defined by the equation x&y=x·y/(x+y) for all [#permalink]

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New post 21 Mar 2017, 11:23
Bunuel wrote:
If the operation x&y is defined by the equation x&y=x·y/(x+y) for all x≠−y, then (18)&(9)=

A. 2
B. 3
C. 6
D. 9
E. 12


\(x&y=x·y/(x+y)\)

Or, \(\frac{(18)&(9) = 18*9}{( 18 + 9 )}\)

Or, \((18)&(9) = \frac{162}{27}\)

Or, \((18)&(9) = 6\)

Thus, answer must be (C) 6
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Re: If the operation x&y is defined by the equation x&y=x·y/(x+y) for all [#permalink]

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New post 21 Mar 2017, 15:49
This one is ridiculously easy.

18 x 9/18 +9
162/27
6

Answer is C
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Re: If the operation x&y is defined by the equation x&y=x·y/(x+y) for all [#permalink]

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New post 23 Oct 2017, 01:09
Does anyone get why does statement mentions x≠−y.
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Re: If the operation x&y is defined by the equation x&y=x·y/(x+y) for all [#permalink]

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New post 23 Oct 2017, 01:17
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Re: If the operation x&y is defined by the equation x&y=x·y/(x+y) for all [#permalink]

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New post 26 Oct 2017, 15:31
Bunuel wrote:
If the operation x&y is defined by the equation x&y=x·y/(x+y) for all x≠−y, then (18)&(9)=

A. 2
B. 3
C. 6
D. 9
E. 12


(18)&(9) = (18 * 9)/(9 + 18) = (18 * 9)/27 = (2 * 9)/3 = 2 * 3 = 6

Answer: C
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Re: If the operation x&y is defined by the equation x&y=x·y/(x+y) for all   [#permalink] 26 Oct 2017, 15:31
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