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From: nm@hou2b.UUCP
Newsgroups: net.math
Subject: Re: A liar, truth-teller, and random puzzle
Message-ID: <141@hou2b.UUCP>
Date: Mon, 31-Oct-83 13:20:24 EST
Article-I.D.: hou2b.141
Posted: Mon Oct 31 13:20:24 1983
Date-Received: Thu, 3-Nov-83 05:20:18 EST
Organization: Bell Labs, Holmdel NJ
Lines: 26

Let T, L, and R represent a truth teller, a liar, and one who
answers randomly, respectively.  It is known of A, B, and C
that one is T, another is L, and the thrid is R.  The following
procedure determines who is who using 3 yes/no questions.

Ask A: Q1. Does ABC eual either LRT or TLR?

       If he ansers "yes", ask the follwing two questions from B
          Q2. Is 3 an even number?
          Q3. Does A=R?
     
       If the answer to Q1 is "no" ask the same Q2 and Q3 from C.

The followng chart dertermines who is who:


   Q1   Q2   Q3   A   B   C
------------------------------
   Y    Y    Y    T   L   R
   Y    Y    N    R   L   T
   Y    N    Y    R   T   L
   Y    N    N    L   T   R
   N    Y    Y    T   R   L
   N    Y    N    R   T   L
   N    N    Y    R   L   T
   N    N    N    L   R   T