Question

How many zeros are at the end of 100! (100! means 100 * 99 * 98 * 97 * ... 3 * 2 * 1)

Answer 1

there is a formula for this
http://en.wikipedia.org/wiki/Trailing_zero

Answer 2

tell me if you need help implementing that formula for n=100

Answer 3

see the example of 32! given there too.

Answer 4

basically you'll just need to do
|_ (100/5) _| + |_ (100/5^2) _| =...

Answer 5

and since 100 is a multiple of 5
it'll just be
(100/5 + 100/25) =...

Answer 6

do you still have any doubt on how to find number of zeros at the end ?

Answer 7

yes/no ?