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What is the value of the product of x and y?

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Math Expert
Joined: 02 Sep 2009
Posts: 47161
What is the value of the product of x and y?  [#permalink]

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17 Sep 2017, 03:50
00:00

Difficulty:

35% (medium)

Question Stats:

69% (01:10) correct 31% (01:17) wrong based on 32 sessions

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What is the value of the product of x and y?

(1) x + y = 0
(2) The average of x^2 and y^2 is equal to the smallest positive integer multiple of two.

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Senior Manager
Joined: 02 Jul 2017
Posts: 294
GMAT 1: 730 Q50 V38
Re: What is the value of the product of x and y?  [#permalink]

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17 Sep 2017, 04:29
1
1
What is the value of the product of x and y? => xy ?

(1) x + y = 0
=> y=-x
=> $$xy = x * -x = -x^2$$
Insufficient

(2) The average of x^2 and y^2 is equal to the smallest positive integer multiple of two.
=> $$\frac{x^2+y^2}{2} = 2$$ ( smallest +ve integer multiple of 2 = 2)
=> $$x^2+y^2 =4$$

Insufficient

(1)+(2)

$$x+y =0$$ and $$x^2+y^2 = 4$$

=> $$x^2+y^2 =4$$
=> $$x^2+y^2+2xy =4 +2xy$$
=> $$(x+y)^2=4 +2xy$$
=> $$0 =4+2xy$$
=> xy = -2

Re: What is the value of the product of x and y? &nbs [#permalink] 17 Sep 2017, 04:29
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