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# What is the value of xy ? (1) The average of x and y is 7. (2) The ave

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Math Expert
Joined: 02 Sep 2009
Posts: 50730
What is the value of xy ? (1) The average of x and y is 7. (2) The ave  [#permalink]

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10 Dec 2017, 00:11
00:00

Difficulty:

25% (medium)

Question Stats:

88% (00:45) correct 13% (00:53) wrong based on 40 sessions

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What is the value of xy ?

(1) The average of x and y is 7.
(2) The average of x and -y is 1.

_________________
Manager
Joined: 24 Nov 2016
Posts: 152
Re: What is the value of xy ? (1) The average of x and y is 7. (2) The ave  [#permalink]

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10 Dec 2017, 04:49
Bunuel wrote:
What is the value of xy ?

(1) The average of x and y is 7.
(2) The average of x and -y is 1.

(1) The average of x and y is 7. $$\frac{x+y}{2}=7, x+y=14$$; x=0 y=14 xy=0 or, x=7 y=7 xy=49, not suf.

(2) The average of x and -y is 1. $$\frac{x+(-y)}{2}=1, x+(-y)=2$$; x=0 y=-2 xy=0 or, x=4 y=2 xy=8, not suf.

(3) Combine $$x+y=14, and, x+(-y)=2, 2x=16, x=8$$; substitute x in any equation, y = 6 and xy = 48, sufficient.

Manager
Joined: 16 May 2017
Posts: 52
Location: India
What is the value of xy ? (1) The average of x and y is 7. (2) The ave  [#permalink]

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12 Dec 2017, 15:54
Bunuel wrote:
What is the value of xy ?

(1) The average of x and y is 7.
(2) The average of x and -y is 1.

As per stmt 1:

given average value of x and y is 7; (x+y)/2 =7

hence x+y = 14.possible combination for x & y are (7,7),(13,1),(1,13)..etc..in sufficient,

As per stmt 2:

given average value of x and -y is 1,hence (x-y)=2

possible combination for x and y are (3,1),(4,2)..etc in sufficient

combining both linear eqns.

we can solve linear equations from stmt1 and stmt 2 and find value of x and y

x+y=14 and x-y=1.

hence ans is C IMO
What is the value of xy ? (1) The average of x and y is 7. (2) The ave &nbs [#permalink] 12 Dec 2017, 15:54
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