They then apply this knowledge to working out the perimeter of a rectangle and a square. Zach then displays his favourite window, which is a composite rectilinear shape. The children talk through ...

The area of a shape is the size of its two dimensional surface. When a square measures 1 cm by 1 cm, we say it has an area of 1 cm 2 (centimetre squared). This rectangle covers 15 squares so it ...

So, the planimeter isn’t just measuring the length of the perimeter, but the size of the perimeter. The final measurement is output in square inches.