You heard the travelers’ tales, you followed the maps, and now, you’ve finally located the dungeon containing a stash of ancient coins. The good news: the wizard who owns the castle has generously agreed to let you have the coins. The bad news: he’s not quite as generous about letting you leave the dungeon … unless you solve his puzzle.

Can you solve the dark coin riddle? This lesson was written by Lisa Winer and animated by Artrake Studio about a brainteaser that’s often called ‘The Coins in the Dark’ riddle, as seen in The New York Times. Try this version with fewer coins:

You are blindfolded and 10 coins are placed in front of you on a table. You are allowed to touch the coins but can’t tell which way up they are by feel. You are told that there are 5 coins head up, and 5 coins tails up but not which ones are which. How do you make two piles of coins each with the same number of heads up? You can flip the coins any number of times.

If you like brainteasers, we also recommend the One Minute Mysteries book series featuring 65 Short Mysteries You Solve With Science! and with Math!

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