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Math Moment - Coin Balance Solution

Here's how to solve this math forum coin balance problem in two steps.

First weighing

Put three coins on each side of the balance.

If one side is heavier, one of the three coins on that side must be the bad coin. So put the three on the lighter side on the "good" platform at the top left part of the game. Also, the three coins you didn't weigh must also be good, so move them to the "good" platform.

If the two sides are equal in weight, the bad coin must be in the three you didn't weigh. So move all the coins on both sides of the balance to the "good" platform.

Second weighing

Put a coin from the remaining three coins on each side of the balance and weigh. If one is heavier, it must be the bad coin. If they balance, the coin you didn't weigh is the bad coin.

More Fun Math for Kids



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