The Five Hats
Three men are being held prisoner. Let's call them Abel,
Baker and Charlie. One day, a guard walks into their cell carrying five
hats. Three of the hats are red, and two of the hats are white. The guard
puts one hat on each prisoner's head. They cannot see their own hat, or
the two hats the guard has left.
The guard says, "If any one of you can tell me what colour
hat you have on your head, you can all go free."
Abel looks at the other two and says, "I don't know."
Baker looks at the other two and says, "I don't know."
Charlie, who is blind, tells the guard what colour hat
he has on his head, and explains how he knows.
What colour hat did Charlie have on his head, and
how did he know?