Here are three everyday things: a triangular yield road sign, a four-pane window, and a six-sided warning sign.

Hands up: how many straight sides does each one have? And what do we call the pointy corners where two sides meet?

Four shapes on the board, one at a time. For each one, count the straight sides with me, then the corners. The corners where two sides meet are also called vertices.

Let's mark these up together on the board. First a pentagon. Then a hexagon. Then an eight-sided shape. Last, back to that eight-sided shape, but this time count the corners instead of the sides. For each one, say how many sides and corners you expect. Then a pupil taps to number the sides and dot the corners so we can check.