Circumference of a Circle

The circumference is the perimeter of a circle: \(C = \pi d\), or \(C = 2\pi r\) when the radius is given. In NSW Year 8 maths (NESA outcome MA4‑LEN‑C‑01) answers are given exactly in terms of \(\pi\), such as \(16\pi\) m, or rounded using the \(\pi\) key on a calculator.

You will find circumferences from a radius or diameter, work backwards to the diameter or radius, and find the perimeter of semicircles and composite shapes such as a running track with curved ends. You will also find the length of the label around a tin, count the turns a bike wheel makes in a kilometre, size a trundle wheel and find a tree trunk's diameter from a tape measure. It is part of Year 8 Area and Perimeter.