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by [email protected] » Tue Jul 29, 2014 11:34 pm
Hi leekaru14,

It's a good idea to TEST VALUES on a question such as this.

You mention W = 4, X = -2, but did you do the rest of the work.....

We're told that WX = Y. We're asked for the value of XY.

Fact 1: WX^2 = 16

If W = 4, X could = 2 or -2, so I'll walk you through both possibilities.

W = 4
X = 2
Y = 8
XY = 16, so the answer to the question is 16

W = 4
X = -2
Y = -8
XY = 16, so the answer to the question is 16

If W = 16, X could = 1 or -1....

W = 16
X = 1
Y = 16
XY = 16, so the answer to the question is 16

W = 16
X = -1
Y = -16
XY = 16, so the answer to the question is 16.

The answer to the question is always 16, so Fact 1 is SUFFICIENT.

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by GMATinsight » Wed Jul 30, 2014 6:21 am
thedude232 wrote:If wx=y, what is the value of xy?

(1) w(x^2) = 16

(2) y = 4

Thanks!
Given : wx = y

Question : xy = ?

Statement 1) w(x^2) = 16
i.e. (wx) * x = 16
i.e. y * x = 16
SUFFICIENT

Statement 2) y=4
Doesn't give us any clue about x therefore INSUFFICIENT

Answer: Option A
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by jaspreetsra » Mon Dec 29, 2014 1:11 am
If wx = y, what is the value of xy?

1. w(x^2) = 16
2. y = 4

Question Stem:
xy = y^2/w

St 1
w=16/x^2
So, xy = (y^2) *(x^2/16) =>xy = 16 Sufficient
St 2
y=4 Not sufficient
IMO:A
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by nikhilgmat31 » Mon Aug 31, 2015 4:08 am
There are two ways to solve this question, either

wx = y
multiplying x on both sides - x can be +ive or -ive will not matter since we are dealing with equality symbol.

wx * x = x * y = 16
xy = 16

answer A.

other way is to substitute values for w & x for wx^2 = 16 & get value for xy which come 16 always.

answer A.
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by Max@Math Revolution » Wed Sep 02, 2015 9:34 pm
Forget conventional ways of solving math questions. In PS, IVY approach is the easiest and quickest way to find the answer.


If wx=y, what is the value of xy?

(1) w(x^2) = 16

(2) y = 4
transforming the original condition, wx=y--> since the question asks for xy, xy=x(wx)=wx^2=?. Therefore the answer is A.


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