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by sogmat » Thu Dec 18, 2008 6:58 pm
If 2^x + 2^x + 2^x + 2^x = 2^n, what is x in terms of n?
A. n/4
B. 4n
C. 2n
D. n - 2
E. n + 2
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by vishubn » Thu Dec 18, 2008 7:00 pm
2^x(1+1+1+1)
2^x*2^2

2^x+2=2^n

n=x+2

x=n-2

D

vishu
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by VP_Jim » Fri Dec 19, 2008 7:42 am
Another good way to do this problem is to plug in numbers for x. If we plug in 2 for x, we get:

16=2^n
So, n = 4

If n=4 and x=2, x in terms for n is answer choice D, n-2.

Note that plugging in any number will work - x=1, x=3, etc.
Jim S. | GMAT Instructor | Veritas Prep
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