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Thread: Tylenol Riddle

  1. #1
    Gold Lounger Maudibe's Avatar
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    Tylenol Riddle

    Fictional scenario:

    You have twelve acetaminophen tablets that ALL LOOK THE SAME. You must take one of them to help you get rid of a headache or you will die. Because of your recent inheritance, someone has tampered with the bottle. You know eleven of them are lethal and only one will help you. The "good" tablet is either LIGHTER OR HEAVIER than the other eleven.

    To assist you, you are given a scale. However, this scale will break after the third use. (The scale is like the scale of justice.)

    How do you determine the good acetaminophen tablet?

    PS: The removal or addition of a tablet counts as use of the scale.
    Last edited by Maudibe; 2014-12-29 at 05:56. Reason: Removed Brand name and replaced with generic

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    Super Moderator BATcher's Avatar
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    "Other effective headache remedies are available" should have appeared as a footnote to the problem!

    (BTW Tylenol is unknown in the UK - we use the generic name paracetemol, or some other proprietory name.)
    BATcher

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    Good question, I'd like to see the answer; once through I can only figure 4 measures and even then there's a 66% chance of needing a 50/50 guess between two.

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    I'm sure this is part of a Mensa test. I'm also sure I don't know the answer.

    cheers, Paul

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    Super Moderator CLiNT's Avatar
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    Dump the Tylenol and take Motrin instead.
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    Invest a little time and energy in a well thought out BACKUP regimen and you will have minimal down time, and headache.

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    Super Moderator Rick Corbett's Avatar
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    1. Divide the 12 tablets into 4 piles of 3.
    2. Place 2 piles of 3 on the left scale and 2 piles of 3 on the right scale. (use 1)
    3. Discard both piles of 3 on the heavier side of the scale.
    4. Move one pile of 3 to the empty side of the scale. (use 2)
    5. Discard the pile of 3 on the heavier side of the scale.
    6. Remove 1 pill and keep it in your hand, move another pill to the empty side of the scale so each side of the scale has one pill. (use 3)

    If the scale remains perfectly balanced then the pill in your hand is the genuine one. If one side of the scale dips down then the scale on the lighter side holds the genuine pill.

    Easy-peasy lemon squeezy.

  7. #7
    Silver Lounger
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    That makes sense...I was using the wrong scale in my mind.
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    WS Lounge VIP access-mdb's Avatar
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    If the pill can be lighter as well as heavier, why would step 3 work?

  9. #9
    Super Moderator Rick Corbett's Avatar
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    Quote Originally Posted by access-mdb View Post
    If the pill can be lighter as well as heavier, why would step 3 work?
    Oops... ROFL

  10. #10
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    One can swap the groups it seems by those rules (none are removed) and determine which group the odd pill is in, doesn't matter which way it weighs. Remove all but two of those remaining, palming the third of the group. If it balances you're holding the good pill, if not, swap one, if then it balances, you now hold the good pill, if not, chug the the other one with a glass of water.

  11. #11
    Gold Lounger Maudibe's Avatar
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    F.U.N,

    Each swap requires a new weigh

  12. #12
    Silver Lounger
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    I don't know then, not knowing if it's heavier or lighter throws a spanner right into my main brain gear.

  13. #13
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    Now what did I do with that 13/16" AF spanner I used to check that custs' diff oil? Bang-crash, uh-oh here comes cust back with dirty look on face. Oh, so that is what happened to that spanner...
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