nguyendinhtuong wrote:
The value of \(3^{-2} + 3^{-4} + 3^{-6}\) is how many times the value of \(3^{-5}\)?
A. \(\frac{91}{3}\)
B. 27
C. \(\frac{31}{3}\)
D. 3
E. \(\frac{1}{3}\)
Source: GMAT Free
Let's factor out \(3^{-5}\)
We get: \(3^{-2} + 3^{-4} + 3^{-6} = 3^{-5}(3^3 + 3^1 + 3^{-1})\)
\(= 3^{-5}(27 + 3 + \frac{1}{3})\)
\(= 3^{-5}(30 + \frac{1}{3})\)
\(= 3^{-5}(\frac{90}{3} + \frac{1}{3})\)
\(= 3^{-5}(\frac{91}{3})\)
Answer:
Cheers,
Brent
_________________
Brent Hanneson – GMATPrepNow.com
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70% (02:10) correct 
