1. The problem statement, all variables and given/known data This is not a homework problem. I was just wondering the logic and intuition behind the "formula" for finding the number of zeros given the factorial of a number. 2. Relevant equations Formula : round(n/5) + round(n/25) + round(n/125)+.......+round(n/5^n) Here, round function indicates that only the integer part of (n/5^n) should be taken. Example1 : Say if you want to find the number of zero's in 5! ?? Usage : In this case n = 5. -> round(5/5) + round(5/25)+.... ->round(1) + round(0) -> 1 (1 zero in 5!) Example2 : find the number of zero's in 130! ?? Usage : In this case n = 130. -> round(130/5) + round(130/25) + round(130/125) .... ->round(26) + round(5) + round(1) -> 32 (32 zeroes in 130!) Thanks!!