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If x*y*z=0, what is the value of z/y*y? (1) x=3*y/4, (2) [#permalink ]
13 Jan 2005, 00:20

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If x*y*z=0, what is the value of z/y*y? (1) x=3*y/4, (2) z=2*x/3

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I got it as C.

z/y*y = z (by applying PEMDAS)

So, we need to find out the value of z.

I is not sufficient because two equations and three variables.

II is not sufficient because two equations and three variables.

But, I and II together have three equations (along with xyz = 0) and three variables.

z = 2x/3 => x = 3z/2

x = 3y/4 => y = 4x/3 = (4/3) (3z/2) = 2z

xyz = 0 => 3z/2 * 2z * z = 0 => 3*(z^3) = 0 => z = 0;

So, I and II are sufficient together. => The answer is C.

MoscowFuturist wrote:

If x*y*z=0, what is the value of z/y*y? (1) x=3*y/4, (2) z=2*x/3

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Chandra

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Sorry, may be I uncorrectly write the problem
If x*y*z=0, what is the value of z/(y*y)? (1) x=(3*y)/4, (2) z=(2*x)/3.

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Then I am getting it as E. as z/(y*y) = 1/4z (by plugging in I and II) and z = 0. 1/4z cannot be found out.

MoscowFuturist wrote:

Sorry, may be I uncorrectly write the problem If x*y*z=0, what is the value of z/(y*y)? (1) x=(3*y)/4, (2) z=(2*x)/3.

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Thnx & Rgds,
Chandra

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My answer is D, but GMAT Plus Answer is E. With whom do you agree?
My reasoning is that division by y means that y is not zero. 1 or 2 suggest that both x and z are zero.

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If the question said: y cannot be 0, then the answer would be D (z=0), but as it is written it doesnâ€™t make sense:
(1) insuff. Either z=0 or x=y=0, but this makes no sense
(2) either x=z=0 or y =0
x=z=0 can happen, but y=0 makes no sense.
(1+2) x=y=z=0 No sense
So for me the answer is: badly written question, donâ€™t bother!
If the question were: x*y*z not equal 0, then,
1. insuff,
2. insuff,
1+2: (z/y*y) = 1/4z insuff
Therefore E

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I donot think we can conclude that y != 0 unless the stem says so. Anyway, this is very tough query!!

MoscowFuturist wrote:

My answer is D, but GMAT Plus Answer is E. With whom do you agree? My reasoning is that division by y means that y is not zero. 1 or 2 suggest that both x and z are zero.

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If x*y*z=0, what is the value of z/y*y = A ?
1st statement : x=3*y/4
Either z = 0 and/or (x or y = 0) problem is this ratio can be undetermined (possible answers are 0, +/- infinite, or 0/0)
So I do not know how to conclude
2nd statement : z=2*x/3
IMO same pb as the above one (y=0 or z=0)
Both statements : x=y=z=0, then A has no value.
I pick E.
Is this one from serious material ?

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I met this question in GMAT Plus, Set 1.

I think that this question refers to "know more - think more" principle