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Path: utzoo!watmath!clyde!cbosgd!ihnp4!mhuxt!js2j
From: js2j@mhuxt.UUCP (sonntag)
Newsgroups: net.puzzle
Subject: Re: A different weighing problem
Message-ID: <801@mhuxt.UUCP>
Date: Mon, 22-Apr-85 17:35:42 EST
Article-I.D.: mhuxt.801
Posted: Mon Apr 22 17:35:42 1985
Date-Received: Tue, 23-Apr-85 07:14:02 EST
References: <13940@watmath.UUCP> <788@mhuxt.UUCP> <236@athena.UUCP>
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 29

> > > You are given, say, 100 bags of 100 coins each; one of the bags contains
> > > counterfeit coins, which weigh, say, 10% less than the real coins.
> > > You must determine, in ONE weighing, which bag contains the counterfeits.
> > 
> >     Easy!  Just pile up 1 coin from bag #1, 2 coins from bag #2, ..., and
> > 100 coins from bag #100.  Weigh the entire pile together.  Subtract this
> > weight from the weight of (100 triangular (100+99+98+..+1)) real coins.
> > Divide this difference by the difference in weight between real and
> > counterfiet coins.  The result is the number of the bag containing the
> > counterfiet coins.
> > 
> >     I'm assuming that you know pretty accurately just what a single real
> > coin and a single counterfiet coin weigh.  
> 
> I have used this as an example of the difference between puzzle solving
> and problem solving.
> The mathematics is easy, but the pragmatics of counting out those coins
> and keeping track of exactly which 37 coins came from bag 37, etc,
> makes the clever solution rather impractical.
> 
> Rik Smoody

    Who said anything about keeping track of which coins came from which bag?
Certainly not me.  I was just planning on dumping them into one big pile.  Do
you understand how this solution works?
-- 
Jeff Sonntag
ihnp4!mhuxt!js2j
    "But if we took out the bones, it wouldn't be crunchy, now, would it?"