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by Perminology » Sat Oct 31, 2009 6:50 am
Did a practice test last night and this question really got to me

5^21 X 4^11=2X 10^n, n=?
11
21
22
23
32

Sat infront of the question for some time, and just chose 32 knowing it was wrong. Any one have a take on this?
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by satish.nagdev » Sat Oct 31, 2009 7:30 am
should be 21
5^21 * 4^11 = 2 * 10^n
==> 5^21 * (2^2)^11 = 2 * (2^n * 5^n)
5^21 * 2^22 = 2^(n+1) * 5^n
so matching power of 5, n=21

whats o.a
Wounded by GMAT but not dead
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by Perminology » Sat Oct 31, 2009 12:11 pm
You are completely right. Thanks for the help!
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