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The false coin problem

  1. Jan 9, 2015 #1
    There are 12 coins, 1 of which is false, you do not know if the false coin weighs more or less than the other 11, you have a balance scale which balances one side with the other. You have 3 weighs to guarantee finding which is the coin. I have asked the smartest people I know and so far no one has solved it.
    If you do have an answer please start a conversation with me and I will tell you if its correct or not. So as not to spoil it for anyone viewing this. Just post, "I have sent you my solution" or something.
     
  2. jcsd
  3. Jan 9, 2015 #2

    phinds

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    We have a "spoiler" capability so that people can post their answer and others don't have to see it if they don't want to. If you already know the answer, why are you posting the question? What's your point?
     
  4. Jan 9, 2015 #3
    It was one of the most rewarding problems, The feeling I got when I finally came up with the answer, it took me 3 days of thinking about this problem just wanted to share it. Maybe I just want to brag, but honestly I don't feel like I solved it, I went to bed and when I woke up the answer was in my mind. Basically its a cool problem it makes you think different. And few people ever have the patience to solve it.
     
  5. Jan 9, 2015 #4
    It probably would have been better for me to not know the answer. How do I turn on this spoiler thing?
     
  6. Jan 9, 2015 #5

    phinds

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    You use the spoiler tags, which consist of that word inside square brackets with a leading forward slash inside the ending tag
     
  7. Jan 9, 2015 #6
    When writing it I thought I would make this problem seem hard to people by stating a true fact, that all the smartest people I have asked have been unable to solve it.
    On further inspection I was definitely bragging, and to be honest I do feel proud of myself for having the thought come into my head of the solution to this problem, though I feel it would be best if I didn't feel that way. The funny thing is I bet some sixth grader might read this problem and solve it in a matter of minutes. Then I will have a choice to either feel dejected or to feel a mixture of still pride in myself and a slight hatrid for that know-it-all kid.
     
  8. Jan 9, 2015 #7

    phinds

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    We have a section for "fun photos and games" and had you posted it there, I would not have questioned why you posted it (I DID assume you were bragging) but you posted it in the math area which is why I asked.
     
  9. Jan 9, 2015 #8
    I thought it related to the topic of logic.
     
  10. Jan 9, 2015 #9
    Probably best to move it.
     
  11. Jan 11, 2015 #10

    Jonathan Scott

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    This is a well-known puzzle, for which there have been several threads here - see the "Similar threads" section below this thread.

    I just worked it out again for myself and then checked my answer against the Wikipedia article on balance puzzles which includes a specific section on "The twelve-coin problem".
     
  12. Jan 11, 2015 #11
    Oh, my bad. lol, this thread has had the opposite intention of why I posted it, I wanted to prove how smart I was. Not smart at all. Still a good problem though. I imagine a series of posts of people who solved the problem between sips of their morning coffee.
     
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