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by grandh01 » Thu Aug 30, 2012 10:18 pm
For all real numbers v, the operation
v* is defined by the equation v* = v - v/3 . If (v*)* = 8, then v =
(A) 15
(B) 18
(C) 21
(D) 24
(E) 27

OA is B
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by adthedaddy » Thu Aug 30, 2012 10:56 pm
(v*)* = (v-v/3)-[(v-v/3)/3] = (2v/3) - (2v/9) = 4v/9
Now given that (v*)* = 8
4v/9 = 8
Therefore, v=18
Option: B
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by atul1729 » Thu Aug 30, 2012 10:56 pm
as v*=v-v/3
(v*)*=v*-v*/3 = v-v/3-{(v-v/3)/3}=8
=>v-v/3-v/3+v/9=8
=>(10v-6v)/9=8
=>v=18

ans option B
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by Brent@GMATPrepNow » Fri Aug 31, 2012 5:08 am
The two above solutions are perfect, but I thought I'd point out that plugging in the answer choices might be a fast approach as well.

Cheers,
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by mohan514 » Fri Aug 31, 2012 9:14 am
made a calculation mistake here....

3v-v if not substituted with 2v is giving me an error

m not sure where i am making the mistake
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