Today's Question - Of seven coins, which all look alike, five have the same weight while two are slightly heavier. Using a balance scale of two pans, without weights, how many operations are necessary to tell which are the two heavy coins?

Reveal Answer Answer - Take 6 of the 7 coins and put 3 on each side of the scale. If they balance then there is one heavy coin in each set. Then take 2 coins from a set and if they balance the odd one if the heavy. If the 3 vs. 3 does not balance then the heavy set contains the coin. Etc. Etc. So you should only need 3 weighings.

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