Perimeter

Perimeter is the distance all the way around a shape, so every side is added once and all lengths must be in the same unit. In NSW Year 8 maths (NESA outcome MA4‑LEN‑C‑01) it covers trapeziums, kites, rhombuses, regular polygons and composite shapes in which every corner is a right angle.

You will find missing sides in L-shapes and staircases, write a perimeter as an expression such as \(x + (x + 3) + 2x\) and solve for \(x\), and work backwards from a perimeter to a side. You will also cost fencing for a yard with a gate and a house wall, buy skirting boards sold in fixed lengths, and see why the same five squares can make shapes with different perimeters. It is part of Year 8 Area and Perimeter.