Perimeter, Area, and Volume

Measurement questions feature prominently on the CSSE 11+ maths paper. You need to be comfortable calculating the perimeter and area of 2D shapes, as well as the volume and surface area of 3D shapes. The CSSE often tests these skills through multi-step problems — for example, finding the area of a compound shape or working backwards from a given area to find a missing length.

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Perimeter

Perimeter is the total distance around the outside of a 2D shape, measured in units of length (cm, m, km, etc.).

Perimeter Formulas

Shape	Perimeter formula
Rectangle	2 × (length + width)
Square	4 × side
Triangle	side a + side b + side c
Circle (circumference)	pi × d or 2 × pi × r

Worked Example

A rectangle is 14 cm long and 9 cm wide. What is its perimeter?

• Perimeter = 2 × (14 + 9) = 2 × 23 = 46 cm

Compound Shape Perimeters