Measuring circles

Students measure the circumference and diameter of round objects and discover the number pi.

Steps

1. Students bring round objects: a plate, a tin, a mug, a lid.
2. In pairs, they measure each object's circumference with string and its diameter with a ruler.
3. They record the results in a table and divide the circumference by the diameter on a calculator.
4. Compare the results: everyone gets about 3.14.
5. Contest: who can remember the most digits of pi (with the help of a rhyme).

Tip: At the end you can eat round biscuits, with every piece described as a fraction.

Materials needed

• Cotton string (1 ball)
• 30 cm rulers (1 per pair)
• Calculator (1 per pair)