Question

Find the number of consecutive zeros at the end of 72?

Answer 1

Well since there are enough even numbers going around, you get one zero when you multiply by a multiple of 5.  

You'll also get two zeros (that is one extra zero) when you multiply by a multiple of 25.  

Between 1 and 72 there are 14 multiples of 5 and 2 multiples of 25.  

That gives you 14+2 = 16 zeros.