A group of five people want to put a set of locks on a chest and distribute keys to the locks amongst themselves in such a way that all the locks on the chest could be opened only when at least three of them were present to open it.

How many locks would be needed, and how many keys?

So, there're five people. If each of them is to have a key for a certain lock, the keys should be five.
Does 'how many keys' mean that if two persons' keys open the same lock that's viewed as one key, or does it mean that some men may be left keyless? Otherwise, this part of the question seems pointless to me.

Posted by George on 2004-03-03 17:56:20