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Exponent Question--GMAT Prep

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Source: — Problem Solving |
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by RM » Sat Jul 28, 2007 10:09 am
You can factorize the equation to its prime factors.

5^21 x 4^11=2 x 10^n
5^21 x 2^22 = 2 x 2^n x 5^n
5^21 x 2^22 = 2^(n+1) x 5^n

We can equate powers of either prime factor 2 or 5.

i.e. 5^21 = 5^n, gives n = 21
Or, 2^22 = 2^(n+1), gives n = 21
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Junior | Next Rank: 30 Posts
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thanks.

by mindruna » Sat Jul 28, 2007 10:31 am
That's so clear. Thank you so much.
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by marvelxx35 » Mon Jul 30, 2007 6:20 am
when given 5^21 * 4^11 = 2 * 10^n,

simplify 4^11 to 2^22 to get, 5^21 * 2^22 = 2 * 10^n.

then, simplify again to get, 10^21 * 2 = 2 * 10^n.

you can clearly see that n = 21.
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