A Puzzle Addict? Love Challenges? We have Visual Puzzles, Logic Puzzles, Physics Puzzles, Math Puzzles, Brain Teaser and Mystery puzzles.

How many consecutive zeros are there at the end of 100! (100 factorial) ?

For Solution SCROLL DOWN...


There are 24 zeros on the end of 100!

One solution would be to work this out and count the zeros, well I've done this so you don't have to. The answer is...
Well now you can clearly just count the zeros but actually working out the number is not practical so we need another plan.

The clever bit here is thinking what numbers when multiplied together will end in a zero.
So the product of what numbers when multiplied ends in a zero:
1. When one of the things being multiplied ends in zero itself
2. A number ending in 5 multiplied by an even number
3. 25, 50 and 75 when multiplied by some of the small numbers available eg (4, 2 and 6) generate an extra zero

Below is tabulated the origin of all the zeros:
100 Factorial

So that's it then there are 24 zeros at the end of 100!