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Factorial question

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Factorial question

by jnellaz » Mon Dec 01, 2008 1:14 pm
How many zeros does 1000! end with?

a) 248
b) 249
c) 250
d) 500
e) 625

[spoiler]Answer: B. 249[/spoiler][spoiler]
[/spoiler]
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by muzali » Mon Dec 01, 2008 3:01 pm
I found a comprehensive solution here:
https://www.rain.org/~mkummel/stumpers/28jan00a.html
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by jnellaz » Tue Dec 02, 2008 6:26 am
Thanks again!
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by cramya » Tue Dec 02, 2008 6:30 am
5*2=10 (more 2's in 1000! than 5's hence 5 is the limiting factor that detremines the number of 0's)

Shortcut:

Divide 1000 by increasing powers of 5 till u get 0 as the quotient

1000/5+1000/25+1000/125+1000/625+1000/625*5

200+40+8+1+0

= 249
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