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number of digits in a factorial

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by krazy800 » Tue Jun 09, 2009 1:02 am
Folks,
How can we determine number of digits for factorial of a number? For example, how many digits are there in 16!? Is there any generalized procedure?

Appreciate your inputs.
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by yogami » Tue Jun 09, 2009 1:11 am
I will be surprised if there is one. And if there is one then you have to memorize it as I won't be able to derive that within 2 minutes in real GMAT unless lightning strikes my brain and I turn into a genius.
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by yogami » Tue Jun 09, 2009 1:18 am
1! to 3! num of digits 1
4! num of digits 2
5! and 6! num of digits 3
and after this through 13! the num of digits is always three less than the factorial i.e. for 13! it is 10 digits...


for 14 and beyond i have no idea and patience to find out ;)
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