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The New Coffee Room

  1. TNCR
  2. General Discussion
  3. Puzzle time

Puzzle time

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  • KlausK Offline
    KlausK Offline
    Klaus
    wrote on last edited by
    #14

    OK, let's see.

    Since there are at most 20 people anyone can shake hands with, the different numbers of the other 21 partygoers must be the numbers from 0 to 20...

    1 Reply Last reply
    • KlausK Offline
      KlausK Offline
      Klaus
      wrote on last edited by Klaus
      #15

      What I don't understand is how Ms. Klaus plays any designated role in your puzzle that would allow me to distinguish her from anyone else.

      Let's say we name the other 21 persons p-0 to p-20, whereby p-0 shook 0 hands, p-1 shook 1 hands etc.

      Ms. Klaus could be any p-i without raising a contradiction.

      So, let's say Ms. Klaus is p-7 and shook hands with 7 other people. If the puzzle is well-designed, that should lead to some kind of contradiction. But I don't see a contradiction.

      1 Reply Last reply
      • KlausK Offline
        KlausK Offline
        Klaus
        wrote on last edited by Klaus
        #16

        Hm, wait a minute.

        The guy with the 20 handshakes, p-20 must have shaken Ms. Klaus hand because he shook everyone's hand except his own partner's.

        So Ms. Klaus cannot be p-0. And p-20's partner must be p-0, by the same argument.

        Presumably this is the base case of some kind of inductive argument...

        But on the other hand, what prevents Ms. Klaus from being p-20? Hmm...

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        • KlausK Offline
          KlausK Offline
          Klaus
          wrote on last edited by Klaus
          #17

          Ah, I think I got it.

          p-20 must have shaken my hand and hence cannot be Ms. Klaus.
          p-20's partner must have been p-0, who can hence also not be Ms. Klaus.

          p-19 must have shaken my hand, too, because he didn't shake p-0's hand, hence p-19 cannot be Ms. Klaus either.
          By the same argument as above, p-19's partner is p-1, who also cannot be Ms. Klaus.

          If we continue in the same way until p-11 and p-9, we see that the only number that is left is p-10.

          Ms. Klaus shook 10 hands.

          Correct?

          1 Reply Last reply
          • jon-nycJ Offline
            jon-nycJ Offline
            jon-nyc
            wrote on last edited by
            #18

            No, your first statement is not correct.

            Hint - first find out how many hands you shook.

            Only non-witches get due process.

            • Cotton Mather, Salem Massachusetts, 1692
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            • KlausK Offline
              KlausK Offline
              Klaus
              wrote on last edited by Klaus
              #19

              Oh, I see. I think my solution is still correct.

              p-20 must be married to p-0, ..., p-11 must be married to p-9.

              Hence my wife can't be any of p-0,...,p-9 or p-11 to p-20, because I'm not among the ones they are married to.

              That leaves only the p-10 spot for her.

              1 Reply Last reply
              • KlausK Offline
                KlausK Offline
                Klaus
                wrote on last edited by Klaus
                #20

                Here's the full solution.

                p-0 : {}
                p-1 : {p-20}
                p-2 : {p-19,p-20}
                ...
                p-9 : {p-12,....,p-20}
                p-10 = Ms. Klaus : {p-11,...,p-20}
                p-11 : {Mr. Klaus, Ms. Klaus, p-12, ..., p-20}
                p-12 : {Mr. Klaus, Ms. Klaus, p-9, p-11, p-13, ..., p-20}
                p-13 : {Mr. Klaus, Ms. Klaus, p-8, p-9, p-11,p-12, p-14, ..., p-20}
                ...
                p-20: {Mr. Klaus, Ms. Klaus, p-1, .., p-9, p-11,...,p-19}
                Mr. Klaus: {p-11,...,p-20}

                Is this not correct?

                1 Reply Last reply
                • Doctor PhibesD Offline
                  Doctor PhibesD Offline
                  Doctor Phibes
                  wrote on last edited by
                  #21

                  Typical German. You should just ask her.

                  I was only joking

                  1 Reply Last reply
                  • jon-nycJ Offline
                    jon-nycJ Offline
                    jon-nyc
                    wrote on last edited by
                    #22

                    Yes you are right, Klaus

                    Only non-witches get due process.

                    • Cotton Mather, Salem Massachusetts, 1692
                    1 Reply Last reply
                    • KlausK Offline
                      KlausK Offline
                      Klaus
                      wrote on last edited by
                      #23

                      It's a pretty neat puzzle.

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