The Old techInterview Forum

100 factorial

here's a new problem you might find fun. the question is: how many zeroes appear at the end of the rather large number 100!

that's 100 factorial, not yelling the number 100. :)

I recently used your site for studying for a msft interview. Although I didn't get any questions from your site that I hadn't already heard before, it did help to see so many logic problems. thanks! oh, i got the job by the way. :)

Jesse Hersch
Friday, March 22, 2002

and if you find that one too easy, why not find how many zero digits *total* are in 100!

Jesse Hersch
Friday, March 22, 2002

sorry for being redundant. i just found that this question is already on the site! oops.

http://www.techinterview.org/Puzzles/fog0000000149.html

Jesse Hersch
Friday, March 22, 2002

I think the answer to the trailing 0s problem should be 21.

for for for
10s 5s 100
-------------------
10 + 10 + 1

why additional 3 ?? I couldn't understand?

because I think any even number not ending with 0 if multiplied with 5 gives some number ending with 0. If multiplied by 5 again the number of trailing 0s wont increase.

may be my whole understanding of the problem itself is wrong.

comments ...

Govind Jajoo
Friday, March 22, 2002

I take back my posting. I got it now.

thanks for ur patience.

Govind Jajoo
Friday, March 22, 2002