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algebra-average

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algebra-average

by vscid » Sat Jan 03, 2009 5:25 pm
If w>y, the average of x and y is z, and the average of z and x is w, what is the value of x-w / w-y?

A] 1/4
B] 1/3
C] 1/2
D] 3
E] 4
The GMAT is indeed adaptable. Whenever I answer RC, it proficiently 'adapts' itself to mark my 'right' answer 'wrong'.
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Re: algebra-average

by logitech » Sat Jan 03, 2009 5:40 pm
x+y = 2z
z+x = 2w

x-w / w-y?

Lets insert w and y in this equation

x - [(z+x)/2]
------------------------
[(z+x)/2] - ( 2z-xx)


x-z/3(x-z)

1/3
LGTCH
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by cramya » Sat Jan 03, 2009 6:47 pm
Plug in and eliminate is an other way

x+y /2 = z ->x+y = 2z and x+z=2w

To find x-w / w-y

x+z=2w
x+ (x+y)/2 = 3w

3x+y = 4w

Equate each of the choices

x-w / w-y = 1/4 - > We wont get 3x+y = 4w

x-w / w-y = 1/3 - > We will get 3x+y = 4w BINGO

Done

Choose B)
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by cramya » Sat Jan 03, 2009 6:50 pm
Vsicd,
U seem to post good questions. Whats the source if u dont mind me asking ?

Regards,
CR
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by logitech » Sat Jan 03, 2009 6:57 pm
cramya wrote:
Equate each of the choices
And what if it were the E Cramya ? This can take FOREVER!
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by cramya » Sat Jan 03, 2009 7:05 pm
For this problem the computations are not that exhaustive i.e. to do a cross multiplication of whats given.Just my opinion...

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by vscid » Sun Jan 04, 2009 9:23 am
cramya wrote:Vsicd,
U seem to post good questions. Whats the source if u dont mind me asking ?

Regards,
CR
Of course not!
Source is a site called gmatscore. I find their difficulty level pretty high.
The GMAT is indeed adaptable. Whenever I answer RC, it proficiently 'adapts' itself to mark my 'right' answer 'wrong'.
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