Question 983906
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Weigh 3 balls on each side. If they don't balance, take the three from the heavier side. Put one on each side of the balance. If they balance, the third ball is the heavy one. If they don't balance, the heavier side is the heavy ball.
If the scale balances during the first weighing with 3 on each side, the heavy ball is one of the other two, use the second weighing to determine which.