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Nope. It's ternary in nature. The subproblem of "You have 3 coins, one of which is lighter than the others. On a balanced scale, figure out which one is lighter
by phamilton 8y ago
Nope. It's ternary in nature. The subproblem of "You have 3 coins, one of which is lighter than the others. On a balanced scale, figure out which one is lighter in one weighing." is a good place to start. Just enumerate all 3 possible weighings and you should be able to see the correct approach.
- emilfihlman 8y agoHow do you solve this? ABC, one of them is different weight than the other two (either more or less) Possible ways to weigh them: A v B A not enough information E C is odd one out B not enough information A v C A not enough information E B is odd one out C not enough information B v C B not enough information E A is odd one out C not enough information AB v C AB not enough information E C is odd one out C C is odd one out AC v B AC not enough information E B is odd one out B B is odd one out BC v A BC not enough information E A is odd one out A A is odd one out In all possible ways to weight 3 coins, all have uncertainty which means you cannot deduce which is the odd one out.
- scrooched_moose 8y agoYour OP stated one is lighter, not one is different. It's easier than the 12-coin one different puzzle, but introduces the ternary concept well enough to get you started on the harder problem (there are some other complications to it as well). Weigh 2 coins. If the scales move you've found the lighter coin. If the scales balance, it's the third coin you didn't weigh.
- emilfihlman 8y agoAh I got the original (12 coins, one is lighter or heavier) mixed up with 3 coins (one is lighter).
- deleted 8y ago[deleted]
- grive 8y agoLabel each coin, divide in three stacks each time, and shuffle meaningfully each time the subsets, to remove uncertainty.