8 Pennies, 7 Weigh The Same In Less Than 3 steps

You are given 8 pennies, 7 of which weigh exactly the same, but one penny weighs less than the other 7. You also have a judge scale. Find the one penny that weighs the least in less than 3 steps.

-- Dived to 3 pieces

First, you split the 8 pennies into 3 groups of pennies – 2 groups with 3 pennies each and 1 group with 2 pennies. Then, you compare the weight of the first two groups of 3 pennies each by putting them on the scale.

Scenario #1: The 2 groups weigh the same. This means the lightest coin is in the group of 2. So, take those 2 pennies and compare them to each other and find the lightest coin.

Scenario #2: The 1st group weighs more than the 2nd group. Take group #2 (3 pennies) and pick any 2 pennies out of that group of 3. If they weight the same, then the third penny is lighter. If they don’t weigh the same then the lighter one is obviously the lightest penny.

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