If xy = 6, what is the value of xy ( x + y )? (1) x y = 5 : DS Archive
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# If xy = 6, what is the value of xy ( x + y )? (1) x y = 5

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Manager
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If xy = 6, what is the value of xy ( x + y )? (1) x y = 5 [#permalink]

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15 Feb 2009, 09:45
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If xy = – 6, what is the value of xy ( x + y )?
(1) x – y = 5
(2) xy^2= 18
Director
Joined: 29 Aug 2005
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Re: DS: How to solve this [#permalink]

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15 Feb 2009, 13:51
1
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pmal04 wrote:
If xy = – 6, what is the value of xy ( x + y )?
(1) x – y = 5
(2) xy^2= 18

B.

Stmt1. Using xy=-6 and x-y=5, solve for x and y.
You will have 2 set of results (y=-3, y=-2; x=2, x=3), which result in 2 values: xy(x+y)=6; and xy(x+y)=-6 Hence, insuff.

Stmt2. Again, using xy=-6 and xy^2=18, solve for x and y. You will have 1 set of results (y=-3; x=2). This results in xy(x+y)=6 Hence, suff.
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Re: DS: How to solve this [#permalink]

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04 Mar 2009, 18:35
xy = -6, what is -6(x+y)

1, x-y = 5, x=y+5
y*y+5y+6=0, solving y = 3 and y = 2, which gives 2 x values. insufficient

2, xy2 = 18
xy*y=18, solving y=-3, which gives x=2

hence b

Last edited by kaushik04 on 04 Mar 2009, 18:58, edited 1 time in total.
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Re: DS: How to solve this [#permalink]

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04 Mar 2009, 18:54
Oops, just realized my mistake.
Re: DS: How to solve this   [#permalink] 04 Mar 2009, 18:54
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