Grade 11 Measurement

Revision of surface area and volume of solids, and what a scale factor does to each.

Gr 11 Term 3 - MeasurementTerm 3 - 1 week (CAPS)

Practise Measurement in the app →

What gets asked

• Calculate the surface area and volume of prisms, cylinders, pyramids, cones and spheres.
• Find the new volume or surface area after every dimension is multiplied by $k$.
• Work backwards from a volume or surface area to a missing dimension.

You must be able to

• Keep surface area (squares of $k$) apart from volume (cubes of $k$).
• For pyramids and cones, find the slant height with the Theorem of Pythagoras first.
• Carry units: cm${}^2$ for area, cm${}^3$ for volume.

Traps that cost marks

• Multiplying the volume by $k$ when every dimension is scaled by $k$. Volume picks up all three dimensions: it scales by $k^3$.
• Using the perpendicular height in a cone's curved surface area. Curved surface area uses the slant height; the perpendicular height belongs to volume.

Worked example