大象传媒

Calculating the volume of a standard solidVolume of composite solids

The volumes of standard 3D solids can be found using specific formulae. In this SQA National 5 Maths revision guide, we'll go through how to work out the volume of a cylinder, sphere, hemisphere, cone, prism, and composite shapes.

Part of MathsGeometric skills

Volume of composite solids

To calculate the volume of a composite solid, simply split it into smaller solids and calculate their separate volumes.

The volumes of each of the individual solids are then added together to give the total volume of the composite solid.

Example

Calculate the volume of the solid shown.

Give your answer correct to 2 significant figures.

Diagram of a composite shape with values 10cm and 6cm

Answer

Diameter = 10m therefore the radius = \(10 \div 2 = 5\,m\)

Volume of cylinder:

\(V = \pi {r^2}h\)

\(V = \pi \times {5^2} \times 6\)

\(V = 471.238...c{m^3}\)

Volume of sphere:

\(V = \frac{4}{3}\pi {r^3}\)

\(V = \frac{4}{3} \times \pi \times {5^3}\)

\(V = 523.598...c{m^3}\)

Volume of hemisphere \(= 523.598... \div 2 = 261.799...c{m^3}\)

\(Total\,volume = 471.238... + 261.799...\)

\(= 733.037...c{m^3}\)

\(= 730\,c{m^3}(to\,2\,s.f.)\)