Surface Area of Frustums

This resource is aimed at KS4 students taking the Higher paper.

The resource consists of two lessons. The first considers finding the surface area of a frustum with a circular base, the second the surface area of a frustum with a square base. Both lessons have a worksheet. Worked solutions to all questions on the worksheets are included in the presentations.

The first lesson starts with revision of finding the area of the curved surface of a cone. Mini white board work teaches the students to find the slant height from the radius of the base and the perpendicular height.

The net of a circular based frustum is presented and finding the area of the curved face is shown to be key. A lot of mini white board work is done to teach students to find the slant height of the larger cone and the slant height of the smaller ‘removed’ cone. The students do an exercise in finding the area of the curved face.

The first lesson ends with students being shown an example of finding the surface area of a frustum and another exercise for students to do.

The second lesson looking at finding the surface area of a square based frustum follows a similar pattern.