You have 8 identical-looking coins, but 1 is counterfeit and lighter than the others. Using a balance scale, what is the minimum number of weighings needed to guarantee finding the lighter coin?
2
First weighing: compare 3 coins against 3. If equal, weigh the remaining 2 against each other. If unequal, weigh 1 from the lighter group against another 1 to isolate the light coin.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Medium. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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