Date: Jan 27, 1999 4:46 PM
Author: Sarah Seastone
Subject: Re: coins problem
See if this helps:

12 coins problem - Frans Faase

http://home.wxs.nl/~faase009/Ha12coins.html

At 3:02 PM -0500 1/27/99, Helena Verrill wrote:

>a little while ago, someone asked the following:

>

>if you have 12 coins, one of which is either

>heavier or lighter than the others, the others all

>being the same weight, how can you determine which

>one it it, and whether it's heavier or lighter, in

>three weighings.

>

>Well, I did't think about this problem until last

>weekend when I heard it for a second time.

>Anyway, it's not too hard to solve, but how about

>what is the minumum number of weighings that you

>need to determine which is the odd one, and whether

>it's heavy or light, from n coins?

>Eg, you can do 3 coins in 2 weighings,

>12 coins in 3, 38 coins in 4 weighings -

>I'd rather ask for what is the sequence a_n

>so that a_n is the maximum number of coins such

>that the odd one can be found (and said to be heavier

>or lighter). I'd guess this starts 3,12,38...

>but I can't find this sequence in Sloanes integer

>sequences, so presumably that means 38 is not the

>max you can do in 4 weighings... Anyone else tried?

>

>Helena

Sarah Seastone

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