Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site eneevax.UUCP Path: utzoo!linus!decvax!genrad!panda!talcott!harvard!seismo!umcp-cs!eneevax!hsu From: hsu@eneevax.UUCP (Dave Hsu) Newsgroups: net.puzzle Subject: Re: A logic(?) Puzzle (SPOILER) Message-ID: <470@eneevax.UUCP> Date: Wed, 1-Jan-86 23:10:36 EST Article-I.D.: eneevax.470 Posted: Wed Jan 1 23:10:36 1986 Date-Received: Fri, 3-Jan-86 03:54:20 EST References: <114@drutx.UUCP> <100@nbs-amrf.UUCP> Reply-To: hsu@eneevax.UUCP (Dave Hsu) Organization: Imperial Widget Research Center, Kingdom of Maryland Lines: 30 Summary: the OTHER spoiler. In article <100@nbs-amrf.UUCP> hopp@nbs-amrf.UUCP (Ted Hopp) writes: >> You're walking along a road and you come to a fork where the road splits >> into two paths, one to the right and one to the left. You don't know >> which way to go, but you must find out. >> You see two people nearby, and you find out that one of them always lies, >> and the other always tells the truth. They know which way to go. >> You can find out which way to go by asking either one of them ONE certain >> question. What is the ONE question? > >Point at one of the roads and ask either one, "If I were to ask you if this >is the road to Xanadu [that's where you're going, right?], would you say >'yes'?" If the answer is "yes", that's the road to Xanadu, regardless of >whether you asked the truth-teller or the liar. > >An interesting philosophical point concerns the nature of a lie. ... >... I don't know how to solve the >puzzle for liars of the deceptive sort. > >Ted Hopp {seismo,umcp-cs}!nbs-amrf!hopp I believe the deceptive solution is: 1) ask "Which road will the other tell me to take" 2) don't take that one. -dave -- David Hsu Communication & Signal Processing Lab, EE Department University of Maryland, College Park, MD 20742 hsu@eneevax.umd.edu {seismo,allegra}!umcp-cs!eneevax!hsu CF522@UMDD.BITNET And then there were none.