Re: physics/pedagogy of coffee-mixing

[Chuck Britton <cvbritton@TELOCITY.COM>]

At 12:47 PM -0400 6/25/00, Ludwik Kowalski,  you wrote about Re:
physics/pedagogy of coffee-mixing:


> John Denker wrote:
>
>  > Suppose you have a cup of coffee and a cup of tea.  In step 1,
>  > you transfer one spoonful of liquid from the coffee-cup to the
>  > tea-cup.  In step 2, you transfer one spoonful of liquid from
>  > the tea-cup back to the coffee-cup. Question:  Is there more
>  > tea in the coffee, or more coffee in the tea?
>
> I never heard this question. So let me show how I would answer.
> Model each cup as an urn with 1000 balls, black for the coffee and
> red for the tea. Suppose one spoonful means 10 balls and that good
> mixing occurs after the first transfer. Also that volumes of coffee
> and tea balls are identical. Pure water balls are white and can be
> ignored in this problem.
>
> After the first transfer we have 990 black balls in one cup and a
> mixture of 1010 balls in another. What happens after the second
> transfer? It is unlikely that the second spoon will contain more
> than one or two black balls. On that basis my answer is that
> there is more coffee in the tea than tea in the coffee.

but isn't it JUST as likely that you are LEAVING 'eight or nine'
black balls behind in the 'white' container as you carry 'eight or
nine' white balls to the black container?

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Chuck Britton                                   Education is what is left when
britton@ncssm.edu                               you have forgotten everything
North Carolina School of Science & Math         you learned in school.
(919) 286-3366  x224                            Albert Einstein,        1936