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Fake Coin Weighing
LogicMedium
15 min
25 pts
Description
Balance scale, find odd coin (heavy/light) in minimum weighings.
Game Rules
You have 12 coins, one is fake (either heavier or lighter). Using a balance scale, find the fake coin in minimum weighings.
Examples
First weighing: 4 vs 4 coins
Based on result, narrow down to 4 coins
Second weighing: 1 vs 1 from suspect group
Third weighing identifies the fake
Hints
Divide and conquer
Use ternary logic (heavier, lighter, equal)
Solution (Click to reveal)
Divide into 3 groups of 4. Weigh group 1 vs group 2. Based on result, narrow to 4 coins. Weigh 1 vs 1. Final weighing identifies fake. Minimum: 3 weighings.