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From: israel@umcp-cs.UUCP
Newsgroups: net.puzzle
Subject: Coin weighing puzzle
Message-ID: <7280@umcp-cs.UUCP>
Date: Mon, 28-May-84 13:30:37 EDT
Article-I.D.: umcp-cs.7280
Posted: Mon May 28 13:30:37 1984
Date-Received: Fri, 1-Jun-84 07:03:02 EDT
Organization: Univ. of Maryland, Computer Science Dept.
Lines: 6

You are given 12 coins and a balance.  Eleven of them are the same
weight.  The other coin is either heavier or lighter.  Your mission,
should you choose to accept it, is to discover which coin it is that
has the non-standard weight, and whether it is heavier or lighter than
the standard weight.  You can use the balance for comparing the weights
of two different groups of coins.  You must accomplish this with three
weighings or less.