p is the symbol used for this special number Pi is its name (Say it as `pie') p comes from working with circles. p is the ratio of the circumference of a circle to its diameter. This means that you can work out p by dividing distance around a circle by the length of its diameter.

It works for every single circle in the world FACT

``May I have a large container of coffee?'' The strange thing is that the answer you get can only ever be approximate - that is, you can never have an exact value for pi. This has fascinated mathematicians for a very long time and they have kept trying to find ways to calculate values for pi that are more accurate. p = 3.14159   26535   89793   23846   26433   83279   50288   41972   ... ``May I have a large container of coffee?''

``Now I will a rhyme construct, By chosen words the young instruct. Cunningly devised endeavour, Con it and remember ever. Widths in circle here you see, Sketched out in strange obscurity.''

To find the circumference and area of a circle The Circle Learning Objective: To find the circumference and area of a circle

Circumference circumference Circumference = π × diameter diameter

Area Area = π × radius × radius = π × radius2 radius area

Circumference is π x diameter Area is πr2

Example 1 Circumference = π × diameter Circumference = π × 4 Find the circumference of this circle circumference Circumference = π × diameter 4cm Circumference = π × 4 = 12·57cm (2 d.p.)

Example 2 Circumference = π × diameter Circumference = π × 16 Find the circumference of this circle circumference Circumference = π × diameter 8cm Circumference = π × 16 = 50·27cm (2 d.p.)

Example 1 Area = π × radius × radius Area = π × 7 × 7 Find the area of this circle Area = π × radius × radius 7cm Area = π × 7 × 7 = 153·94cm² (2 d.p.) area

Example 2 Area = π × radius × radius Area = π × 5 × 5 Find the area of this circle Area = π × radius × radius 10cm Area = π × 5 × 5 = 78·54cm² (2 d.p.) area

Find the circumference and area of this circle Question 1 Find the circumference and area of this circle Circumference = π × diameter Circumference = π × 9 = 28·27cm (2 d.p.) 9cm Area = π × radius × radius Area = π × 4·5 × 4·5 = 63·62cm² (2 d.p.)

Find the circumference and area of this circle Question 2 Find the circumference and area of this circle Circumference = π × diameter Circumference = π × 12 = 37·70cm (2 d.p.) 6 cm Area = π × radius × radius Area = π × 4·5 × 4·5 = 113·10cm² (2 d.p.)