Prisoners and hats

According to the story, four prisoners are arrested for a crime, but the jail is full and the jailer has nowhere to put them. He eventually comes up with the solution of giving them a puzzle so if they succeed they can go free but if they fail they are executed.

The jailer puts three of the men sitting in a line. The fourth man is put behind a screen (or in a separate room). He gives all four men party hats (as in diagram). The jailer explains that there are two red and two blue hats. The prisoners can see the hats in front of them but not on themselves or behind. The fourth man behind the screen can’t see or be seen by any other prisoner. No “communication” between the prisoners is allowed.

Then, prisoner C (see image) either calls out the color of his hat, or says he doesn’t know. After this, prisoner B either calls out the color of his hat, or says he doesn’t know. Similar for prisoner A. If any of the three prisoners can figure out what colour hat he has on his head all four prisoners go free. The puzzle is to find how the prisoners can escape.

File:Prisoners and hats.PNG

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