The Ultimate Riddle

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15 thoughts on “The Ultimate Riddle

  1. Pingback: Egyik kedvenc fejtorom kalai blogjan « Je blogue

  2. daveagp

    There is a related trick I learned of in grad school: tie both of your shoe laces together, then you have to turn your pants inside out. I am grad that one is not available on YouTube!

  3. Gil Kalai Post author

    Ori, well, I remember a dinner 7-10 years ago at New Haven with John Conway demonstrating it and Hillel Furstenberg trying to repeat it, but I think I already knew this even before the dinner. I dont remember for sure.

  4. Gil

    Dear Ori, Coincidences is a tricky subject to study and even to define. (But extremely interesting and rather important.) Whom did you hear this trick from?

  5. Tom

    The simplest way I can explain it is: when you are touching your nose, your arms are crossed and one of them is on top (say the left one). In order for the trick to succeed, the left index finger must be on top of the right index finger. Thus, when you start the trick, you mix your fingers in such a way that the left index finger is below the right one, and it will come up on top when you twist.

  6. Tom

    Equivalently, if the left (resp. right) arm is lower when you start the trick, then the left index finger (resp. right) must also be lower.

  7. Pingback: Mathematical Gymnastics | Combinatorics and more

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