Prisoner

Puzzles about prison escape strategies are a relatively new genre of mathematical challenge, only a few decades old. They emerged from computer science. A ...

Piper will be able to see the faces of both coins. But she will be able to see the faces of the coins. The guard goes through the rigmarole of putting the paper in one of the boxes, and placing a coin randomly on each box. You will marvel at the result when you see it. Piper will be able to see the faces of all coins. She will not be able to see inside the boxes since they are closed. But once Piper goes into that cell she has no communication with Alex, apart from the ‘message’ that she gives by turning over a single coin. The guard will shut the boxes. Piper will see which box the paper is in. A guard comes in and tells them that they are to be set a challenge that may win them their freedom. A prison – a place where access to information is limited – is a perfect venue for puzzles about the efficient communication of information. You will be asked to find a strategy that wins them their freedom.