Area, perimeter and volume

Circles, cylinders, cones and spheres: exact answers in terms of π, then decimals with the right units. About 10 minutes, KS3 / GCSE.

What you will do

1. Length, area, volume. Lengths use plain units (cm). Areas use square units (cm²). Volumes use cubic units (cm³). Getting the unit wrong is the most common lost mark.
2. The circle. Area = r^2 and circumference = 2 r. Leave π in the answer for an exact value.
3. The cylinder. Volume = base area × height = r^2 h.
4. The cone. A cone is a third of the cylinder with the same base and height. Its slant height comes from Pythagoras.
5. The sphere. Volume = 43 r^3 and surface area = 4 r^2.