# [Maths-Education] Not just Ratio and Proportion

**Dick Tahta**
d.tahta@open.ac.uk

*Wed, 10 Oct 2001 08:27:44 +0100*

Has Dave Hewitt played a joker?
>*Let me see now... circumference of a circle is pi multiplied by
*>*diameter. If my diameter is, for example, 11.37cm, in what way
*>*does the image of repeated addition help me with this
*>*multiplication?
*
What is this pi that he is mutiplying by? Not I suppose a rational
approximation for in that case the multiplication would be equivalent to
that of integers and so equivalent to a repeated addition. But what does a
multiplication by an irrational look like? Is this issue related to the
ancient problem of determining the "ratio" of circumference to diameter?
I can certainly see repeated subtractions in a calculation of that.
Dick Tahta