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No . of zeros in n! = ?

Any direct way to find out???

9 Answers

24
eureka123 ·

[\frac {n}{5}]+[\frac {n}{5^2}]+[\frac {n}{5^3}]+.....[\frac {n}{5^n}]

1
Philip Calvert ·

yeah.

basically we can take this till ∞ only adding lots of zeros wont help. :P

21
eragon24 _Retired ·

E_{2}(n!) = \left[\frac{n}{2} \right] + \left[\frac{n}{2^{2}} \right]....

E_{5}(n!) = \left[\frac{n}{5} \right] + \left[\frac{n}{5^{2}} \right]....

THE NO OF ZEROES AT THE END OF n! is min(E_{5}(n!),E_{2}(n!))

23
qwerty ·

wy not directly E10 ????

24
eureka123 ·

@ deepak.. E2>E5 always..so minimum of them will be E5
so no. of zeros =E5

24
eureka123 ·

@qwerty,
10=2*5

21
eragon24 _Retired ·

K eureka.........

23
qwerty ·

oh sorry sorry ....i confused it with something else ...

62
Lokesh Verma ·

Dont go by this formula unless you have understood why...
Sorry for presuming this... but do read these :

http://targetiit.com/iit-jee-forum/posts/help-1697.html
http://targetiit.com/iit-jee-forum/posts/9th-january-2009-1549.html

If you have any doubts, feel free to get clarified :)

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