A Party With Poison Wine
There is a king who wants to throw a party in 48 hours and he wants to serve a total of 240 barrels of wine at the party. Unfortunately, he knows that one of the barrels have been poisoned and he does not know which one. When imbibed, the poison takes up to 24 hours to kill.
In order to determine which barrel the poison is in, the king wants to use his prisoners as taste testers. Now, since he wants to be an example of mercy and kindness in his kingdom, he wants to use the fewest number of prisoners to test the barrels. How many prisoners should he use?
Note: 240 is not necessarily the maximum number of barrels required to test with this number of prisoners.