To work out the area of a circle: Find the value of the radius. If the diameter is given, this must be halved. Substitute the value of the radius into the formula for the area of a circle.

The circumference is the perimeter of a circle. It is a length and so is measured in \(mm\), \(cm\), \(m\) or \(km\). An area is measured in square units: \(mm^{2 ...