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?

(In reply to Cost effective solution by Juggler)

Juggler wrote: "5 Locks and 10 Keys. call the locks A, B, C, D, E. call the Keys 1, 2, 3, 4, 5.

Albert holds lock A and key 1 + a copy of Key 3
Brenda holds lock B and Key 2  + a copy of Key 4
Charlie holds lock C and Keys 3 + a copy of Key 5
David holds lock D and Keys 4 + a copy of Key 1
Eileen holds lock E and keys 5 + a copy of Key 2"

 

Dear Juggler:

How would Albert, Brenda and David unlock the 5th lock ?  

Posted by Penny on 2004-03-03 19:54:15