# The Circumference of a Circle

## Presentation on theme: "The Circumference of a Circle"— Presentation transcript:

The Circumference of a Circle
Teaching Mathematics Visually and Actively The Circumference of a Circle Tandi Clausen-May

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The circumference of a circle

What is  ? First we need  (pi) Is it a number? Is it…..
…...?

Well… not exactly.  is a ratio.

So  is a bit more than 3. once across twice across three times across
Pi is the number of times you must travel straight across the circle to go the same distance as all the way round the circle. Click to see the paths once across twice across three times across and a bit further! So  is a bit more than 3.

How can we be sure that  is a bit more than 3?
2 1 3 For a regular hexagon, the distance all the way round is exactly 3 times the distance straight across the middle. Click to see the paths

Circumference =  × Diameter
And all the way round the circle is a little bit more than all the way round the hexagon. So all the way round the circle is a little bit more than 3 times straight across the middle. Click to see the paths Circumference =  × Diameter

2 1 3 Summary Circumference =  × Diameter Circumference =
times the diameter Click to see the paths …and a little bit more Circumference =  × Diameter

Find it at http://www.uk.sagepub.com
Now watch PP 10-2: The Area of a Circle from the CD inside Teaching Mathematics Visually and Actively Find it at Tandi Clausen-May