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# GMATPrep 1: Question 2

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Senior Manager
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GMATPrep 1: Question 2 [#permalink]  18 Sep 2007, 09:40
Have found it, but cannot explain how...
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Senior Manager
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why it says 'and' in first three answer choices and or in rest????
CEO
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Dacrap can u explain more. i don't get this one.
Manager
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THis is E

Because

xy + z= x ( y + Z)

xy + z = xy + xz

xz - z = 0
z(x-1) = 0

z= 0 ans x= 1
Senior Manager
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beatgmat wrote:
THis is E

Because

xy + z= x ( y + Z)

xy + z = xy + xz

xz - z = 0
z(x-1) = 0

z= 0 ans x= 1

Beatgmat is correct. Now once you reach this equation z(x-1) = 0
we know that x =1 or z = 0 to satisfy the equation
CEO
Joined: 29 Mar 2007
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beatgmat wrote:
THis is E

Because

xy + z= x ( y + Z)

xy + z = xy + xz

xz - z = 0
z(x-1) = 0

z= 0 ans x= 1

Brilliant! Its so simple! I tried plugging in the answer choices. That led me to everything being correct! so i was like wtf is this??? Hate it when I forget to rephrase DS questions.

nice work!
Intern
Joined: 15 Sep 2007
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I got E but did i get it by luck? Would it be wrong to say:

xy + z= x ( y + Z)

then

xy +z = xy +xz

then I thought ok so XY's can be canceled out and we get:

z = xz

which means:

either x is 1 and Z can be whatever.

or

Z = 0 and X can be whatever.

so do we need the z(x-1) = 0 beatgmat mentioned?
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