To get a 0 at the end of the number, you need that number to be multiplied by a 10 or 100 or 1000

10 comes from 5x2

100 comes from 5x5x2x2 and so on

So basically all you have to do is find 5 or powers of 5 since you will easily find an even number to give you a 0

So let's try 5!

The only 5 or power of 5 that divides this number is 5^1 and 5/5 = 1 so there's only ONE 0 at the end of 5!

10! = 10/5 = 2 (we know this to be true)

25! = 25/5 + 25/5^2 = 5 + 1 = 6

So 6 Zeros at the end of 25! (Anybody want to confirm this )

And so on and so forth