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gmat prep

by sneakpeek » Sun Jun 24, 2007 9:08 pm
Each of the numbers w,x,y, and z is equal to either 0 or 1. What is the value of w+x+y+z?

(1) w/2 + x/4 + y/8 + z/16 = 11/16
(2) w/3 + x/9 + y/27 + z/81 = 31/81
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Source: — Data Sufficiency |
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Re: gmat prep

by jayhawk2001 » Sun Jun 24, 2007 9:30 pm
sneakpeek wrote:Each of the numbers w,x,y, and z is equal to either 0 or 1. What is the value of w+x+y+z?

(1) w/2 + x/4 + y/8 + z/16 = 11/16
(2) w/3 + x/9 + y/27 + z/81 = 31/81
1 - Sufficient.
Take the LCM and sum up the numerator
(8w + 4x + 2y + z) / 16
Since w, x, y and z are either 0 or 1, only possible combination
is w=1, x=0, y=1, z=1

2 - Sufficient.
(27w + 9x + 3y + z) / 81
Only w=1, x=0, y=1 and z=1 satisfy the above condition

Is it D ?
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by sneakpeek » Mon Jun 25, 2007 8:31 am
Yes, it is D. Thanks for your response!
Did you just plug in either 0 or 1 to the equation? Is that all I need to do?
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