You have 9 billiard balls. They are all the same weight, save one. You want to find out which one is heavier. All you have is a scale that determines the heavier side. You can weigh any number of balls at any time. What is the least amount of weighings you can do to find the heaviest ball?

correct me if im wrong (and might be the case) but if you got 9 billiard balls all of the same weight wouldnt the answer be 0 : none would be hevier as they weigh the same??

Cool problem. You can do it in two weighings.

Edit - I explained how, but after thinking about it, I took down the explanation in case other people want to puzzle over it themselves.

As a generalization, if you have n balls and one of them is heavy, how many weighings does it take?

I've been thinking about it, and I can't work it out. Pray tell, what be the answer?