If you enjoyed trying out the Four Men in Hats puzzle, here's another one for you. Again, the inmates must solve the puzzle or they will be executed.
On one such occasion, three cells were needed, so three of the cleverest inmates - Albert, Barry, and Carl - were put in a room and given a challenge. A guard showed them 5 party hats - 3 white, 2 black. The guard then removed the hats from view, walked behind each prisoner and placed a party hat on his head. Each inmate could see the two other inmates' hats, but not his own; nor could he see the two extra hats that were not placed on heads.
The guard said, "If anyone can tell me with absolute certainty the color of his own hat, you may all go free. However, under no circumstances may you communicate the color of anyone else's hat."
He first asked Albert. Albert is a very honest and intelligent (ie perfectly rational) person, but he was dumbfounded. "I don't know", he said, "there's no way of knowing."
He then asked Barry. Barry was equally intelligent and rational, but he also could not say.
The guard said, "I regret that I have to execute you three, but seeing as Carl is blind, he's not going to know. You have failed."