gmatprep - exponent

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by selango » Sat Sep 18, 2010 7:10 pm
5^21*4^11=2*10^n

5^21*2^22=2*10^n

2*(5^21*2^21)=2*10^n

2*(5*2)^21=2*10^n

2*10^21=2*10^n

n=21

Pick B
--Anand--