Coins in a Grid
Written on May 8th, 2025 by Sameer Wagh and Paul Cuff
You have an infinite collection of coins on the floor. You are blindfolded but are told that some 20 coins are heads up while the remaining coins are tails up. You can do one of two things – pick a coin and flip it (since you’re blindfolded, you don’t know the orientation of the coin) or pick a coin and toss it out. Can you find a way to ensure that at some point, you have tossed out exactly as many heads as remaining on the floor?
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