Show the L-shape and give five seconds of quiet think-time before hands up. Take two or three answers. Do not confirm the best split yet — that lands in the next step.

Board demo with your pen, not a live interactive reveal. Draw the L and the numbers yourself, then let the class compute.

• Sketch the L-shape. Ask where the split line should go, then draw one straight cut into two rectangles.
• Label A: 6 cm × 4 cm. Class works 6 × 4 = 24 cm².
• Label B: 3 cm × 2 cm. Class works 3 × 2 = 6 cm².
• Cover the total; class predicts, then reveal 24 + 6 = 30 cm².
• Triangle notice: sketch a rectangle, mark a triangle on the same base and height, shade half. Write base × height ÷ 2. This is the idea the house and trapezium rest on later.

Slip to watch: adding side lengths instead of areas, or dropping the cm² unit.

After the worked example, open the interactive in 2D mode only so pupils can drag a rectangle or triangle and read its live area. Do not treat it as the source of the worked numbers.

Try Together board. You draw the split line with the board pen, then the pupil at the board works out each sub-area and the class checks.

For each shape, ask where should the split line go? before you draw it. Then have the class read each sub-area and add them. On the house-shape, hold out for the triangle rule: base × perpendicular height ÷ 2, not the slanting side.

This is a hands-on beat, not the IWB. Hand each pupil (or table) a paper L-shape on squared paper and scissors. Circulate: check the split line is straight and meets a corner, and that sub-areas carry cm² units. Ask a few pupils to show a different split line that gives the same total.

Differentiation: give less confident pupils an L-shape with side lengths already marked; stretch pupils get an unlabelled one they must measure. Fast finishers try a T-shape cut-out (two cuts).