Volume from a uniform cross-section

Volume from a uniform cross-section

Secondary 2
TGM Original — E Math Summary Notes (4052), 2026 editorial manuscript

A prism has two congruent parallel polygonal end faces and a uniform cross-section between them. Its volume is \(V=AL\), where \(A\) is the cross-sectional area and \(L\) is the perpendicular separation of the end faces. Think of stacking equal thin layers.

SolidVolume
Cuboid of length l, width w, height h\(lwh\)
Cube of side s\(s^3\)
Prism of cross-sectional area A and perpendicular length L\(AL\)

Example

A triangular prism has a right-triangle cross-section with perpendicular sides 3 cm and 4 cm, and length 10 cm. Its cross-sectional area is \(\dfrac12\times3\times4=6\text{ cm}^2\), so its volume is \(60\text{ cm}^3\).

For an oblique prism, the sloping joining edge is not the perpendicular separation of the bases. The volume formula uses that perpendicular separation.

Need help? Join our E-Maths tuition for O-Level success.

Learn more