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# If xy + z = x(y+z), which of the following must be true? A.

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Director
Joined: 01 May 2007
Posts: 793
If xy + z = x(y+z), which of the following must be true? A. [#permalink]

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18 May 2008, 18:14
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If xy + z = x(y+z), which of the following must be true?

A. x = 0 and z = 0
B. x = 1 and y = 1
C. y = 1 and z = 0
D. x = 1 OR y = 0
E. x = 1 OR z = 0

My bad, botch the data entry on this one....should have ORs.

Last edited by jimmyjamesdonkey on 18 May 2008, 19:15, edited 1 time in total.
Director
Joined: 23 Sep 2007
Posts: 783
Re: GMATPrep [#permalink]

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18 May 2008, 18:18
jimmyjamesdonkey wrote:
If xy + z = x(y+z), which of the following must be true?

A. x = 0 and z = 0
B. x = 1 and y = 1
C. y = 1 and z = 0
D. x = 1 and y = 0
E. x = 1 and z = 0

xy + z = xy + xz ----> z = xz

the y is not important, so eliminate b,c,d

I think choice E should be "OR" instead of "AND"

E
SVP
Joined: 28 Dec 2005
Posts: 1559
Re: GMATPrep [#permalink]

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18 May 2008, 18:48
why not B ?

if x=1 and y=1, then xy+z = 1+z and x(y+z) = xy+xz = 1 +z
Director
Joined: 23 Sep 2007
Posts: 783
Re: GMATPrep [#permalink]

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18 May 2008, 18:56
pmenon wrote:
why not B ?

if x=1 and y=1, then xy+z = 1+z and x(y+z) = xy+xz = 1 +z

A, B, and E are all correct according to the answer choices.

BUT the original poster did not post the correct answer choices from the real test. There should some "OR"s in the answer choices.
Re: GMATPrep   [#permalink] 18 May 2008, 18:56
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# If xy + z = x(y+z), which of the following must be true? A.

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