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From: markn@ios.UUCP (Mark Nudelman)
Newsgroups: net.math
Subject: Re: a logic brain teaser - (nf)
Message-ID: <164@ios.UUCP>
Date: Mon, 27-Aug-84 16:20:24 EDT
Article-I.D.: ios.164
Posted: Mon Aug 27 16:20:24 1984
Date-Received: Thu, 30-Aug-84 09:25:01 EDT
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>Another possible solution:
>
>"Which way would the other witch say led to dev/null?"  The direction indicated
>would be toward Oz.

Not true.  If "dev/null" means a place which does not exist, the
question "Which way leads to dev/null?" would not be answerable
by the truthful witch; the lying witch could answer with either
direction.  So the proposed question would not get you any information.

Raymond Smullyan has a delightful book full of variations and elaborations
on logic problems of this type, called "What is the Name of This Book?"
I recommend it to anyone interested in logic puzzles.  It has more
variants on the old liar/truth-teller puzzle than you would believe.
At the end he constructs a puzzle whose solution is nearly isomorphic
to the proof of Godel's incompleteness theorem.

	Mark Nudelman
	..decwrl!ios!markn