To calculate the perimeter of a shape, like this window, you can add the length of all the sides together. 100cm + 120cm + 100cm +120cm = 440cm Or, you can multiply the length and width by 2.

In this National 4 Lifeskills Maths study guide, you can revise how to find the perimeter and area of triangles, quadrilaterals (rectangle, parallelogram, rhombus, kite and square), circles, arcs ...