The chessboard puzzle

Today we have prepared a slightly different blog post for you: the checkerboard puzzle.


This is the most interesting prison puzzle we've come across so far. Don't be put off by the certain mathematical "nerd factor". It is surprising that there is a solution at all. What's more, anyone who can count to two can figure it out - once they know it. Therefore it is worthwhile to read on and to puzzle along. So now the question directly to you: What is the solution?

You and an ally (m/f/d) have been caught stealing electricity from an evil criminal blockchain, taken out of the country and imprisoned. You are not facing a trial, but execution. The prison guard wants to pass the time until then and sets you a task that he considers unsolvable. He assumes that he can speed up the execution with it.

The guard will take you to a cell that you have never entered before. In the cell there is a chessboard on which the guard has previously laid out 64 coins purely at random.

The guard will then point to one of the 64 squares and say: "This square is the magic square, the key to your freedom! You must flip exactly one coin, a single coin, heads to tails or tails to heads. After that, I will lead you out of the room into an isolated cell and I will lead your partner in. Of course, he won't have a chance to contact you in the meantime. As usual in such puzzles, any attempt to leave messages or clues other than flipping the coin will not only be punishable by death, but you will have to clean the sanitary facilities first! Your accomplice may only look at the chessboard (not touch it) and must tell me within five minutes which square is the "magic square, the key square". He has exactly one try. If he guesses correctly, you will be released, otherwise you will not live to see the next day. I will not cheat either, but will keep my word."

The jailer explains the rules and then gives you time to come up with a strategy.

If you and your fellow sufferer have solid mathematical foundations and at least one of you has taken a lecture on error correction in, say, computer science, you'll be excellently prepared for an early release.

The only question is how...


As a little hint: maybe you will soon find a solution hint on the Instagram profile of Faktor Zehn ;-)

We are curious how many of you can solve the riddle. The solution will follow the week after next.


Your Faktor Zehn team

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