Weighing Coins
Given are seven outwardly identical coins; four are genuine and three are counterfeit. The three counterfeit coins are of identical weight, as are the four genuine coins.
It is known that a counterfeit coin is lighter than a genuine coin. In one weighing, you can select two groups of coins and determine which is lighter, or if they have the same weight.
How many weighings are needed to locate at least one counterfeit coin?
Difficulty level (1 very easy - 10 very hard): 2
Topics:
Logic
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Reasoning / Logic
Algorithm Theory
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Weighing
Combinatorics
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Case Analysis / Checking Cases
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Processes / Procedures
Minimum and Maximum Problems / Optimization Problems
- Gillis Mathematical Olympiad, 2019-2020 Question 1
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