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# If wx=y, what is the value of xy? 1) wx^2 = 16 2) y=4

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Manager
Joined: 14 Sep 2006
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Schools: Olin Business School - Washington University
If wx=y, what is the value of xy? 1) wx^2 = 16 2) y=4 [#permalink]

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23 Sep 2006, 23:20
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If wx=y, what is the value of xy?

1) wx^2 = 16
2) y=4

Kudos [?]: 58 [0], given: 0

SVP
Joined: 05 Jul 2006
Posts: 1741

Kudos [?]: 418 [0], given: 49

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24 Sep 2006, 00:42
If wx=y, what is the value of xy?

1) wx^2 = 16
2) y=4

from stem

wx=y

from one multiply both sides by x then wx^2 = xy = 16.......suff

from two

y=4 thus wx = 4 x could be any thing .insuff

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Senior Manager
Joined: 05 Mar 2006
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25 Sep 2006, 06:47
X could be '+' or '-', answer should be E cannot determine it.

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Current Student
Joined: 29 Jan 2005
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25 Sep 2006, 08:30
xy could be pos or neg here.

I will take (E)

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Intern
Joined: 25 Sep 2006
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25 Sep 2006, 08:50
I'm picking (A). To flesh out what yezz had posted:

Statement 1:

(i) wx^2 = 16
(ii) w = 16/x^2

plugging into the stem:

(iii) wx = y
(iv) 16x/x^2 = y
(v) 16/x = y since x/x^2 reduces to 1/x

multipling x on both sides yields xy = 16

Regardless of if x is pos or neg, the product xy is always equal to 16, answering the stem, so suff.

Statement 2 is insuff. as plugging 4 into wx = y gives you wx = 4, which won't answer the stem question

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Senior Manager
Joined: 14 Aug 2006
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25 Sep 2006, 09:02
One more for A..

I don't see how the +ve /-ve comes in?

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Manager
Joined: 14 Sep 2006
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Schools: Olin Business School - Washington University

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25 Sep 2006, 10:08
OA is A...damn tough Q.

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SVP
Joined: 05 Jul 2006
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25 Sep 2006, 10:10
GMATT73 welcome back i really sencerly missed you man ... i felt lonely...lets scheduel our next test together i am thinking of early dec ...wut do u think.

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SVP
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25 Sep 2006, 10:18
+ve o -ve has nothing to do with it it is equality of terms

if wx = y multiplying both sides by (x positive or negative it is the same here)

thus wx^2 = xy and whatever the sign of xy (+ve or -ve) we can use the statment to get xy value meaning it is equall to 16

this means w is positive and x we dont know so if we assumed that x is -ve thus sure y is -ve too

and if x is positive thus y is + ve too.

( they gave us the luxury of y being +ve or -ve

I hope am clear

Kudos [?]: 418 [0], given: 49

25 Sep 2006, 10:18
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