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Source: — Problem Solving |
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Re: gmatprep

by parallel_chase » Tue Sep 09, 2008 2:54 pm
ddm wrote:help
5^21 * 4^11 = 2*10^n

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

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

10^21 * 2 = 2*10^n

n=21
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by cramya » Fri Sep 19, 2008 7:21 pm
The key to problems like these are getting the lhs or rhs (depending on which side n is) to match up to find the value of n

Once u get to 5^21 * 2 ^ 21 = 10^21

Formula : (ab)^n = a^n.b^n (as long as n the exponent is the same

In this problem we just reversed it a^n.b^n = (ab)^n
a=2 b =5
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