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if v and w are different integers, does v=0?

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Radar
 Post subject: if v and w are different integers, does v=0?
 Post Posted: Sun May 25, 2008 4:11 pm 
if v and w are different integers, does v=0?
1) vw= v^2
2) w=2




Ans is A
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RonPurewal
 Post subject:
 Post Posted: Wed Jun 04, 2008 7:20 am 
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ManhattanGMAT Staff


Posts: 7146
(1)
make sure you resist the temptation to divide both sides of this equation by v, because you aren't assured that v is nonzero. (in fact, the whole point of the problem is to determine whether that is the case!)
instead, you should move everything over to one side of the equation and factor:
vw - v^2 = 0
v(w - v) = 0
since w and v are not equal, we know that the value of (w - v) is not 0. since the product is 0, this means that the other part of the product (namely v) must be 0.
sufficient

(2)
this is clearly insufficient, since it provides no information about v.

answer = a
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arunchandar
 Post subject: mercury123
 Post Posted: Sun Dec 21, 2008 6:46 pm 
Recently I came across this problem.
I wonder why it is not E.

Consider, v=2 and w=-2
1) vw = v2

Hence v can be 2 or -2 or 0

Both the statements are insufficient...
Am i wrong some where. I am sure answers in OG will not be incorrect.
Can some one please explain.

Thanks!
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RonPurewal
 Post subject: Re: mercury123
 Post Posted: Mon Dec 22, 2008 1:19 am 
Offline
ManhattanGMAT Staff


Posts: 7146
here's the problem.

first, you wrote:

arunchandar@hotmail.com wrote:
Consider, v=2 and w=-2


and then you concluded:
Quote:
Hence v can be 2 or -2 or 0


can't do this. once a variable has a value, it retains that value throughout the rest of the problem.
in other words, since v is assigned to be 2, v can't also be 0 or -2 at the same time.
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