Display the park-map image with the scale bar visible and give five seconds of quiet think-time before any hands go up. Take two or three hands-up answers, not open call-outs. You are only fishing for the idea that the scale bar links paper distance to real distance — do not resolve the maths yet.

Rule stays fixed throughout: paper length times scale number equals real length. Keep place-value talk (times 100 means two zeros) for yourself, not the screen.

Classroom 1:100 — 1 cm on page is 100 cm, one metre, on ground. Plan is 5 cm by 3 cm, so real room 5 m by 3 m. Pull the room in early: if a wall is 4 cm on the plan, how long really? Take two hands before saying 4 m.

Treasure map — 1 cm on page is 10 m on ground; link 10 m back to 1000 cm so the colon ratio 1:1,000 makes sense. For example, 4 cm is 4 times 10 equals 40 m.

Ordnance Survey 1:50,000 — 1 cm is 50,000 cm, half a kilometre. Ask how far 2 cm is, take two hands, then reveal 2 cm times 50,000 equals 100,000 cm equals 1 km. Stress the rule never changes even when numbers get huge.

This round is for talking it through together — pupils take turns at the board and the class agrees or corrects out loud.

Use a stated 6 m × 5 m room (or measure the longest wall and the width to the nearest half-metre). Work the conversion out loud, showing the division each time: 6 m = 600 cm, 600 ÷ 100 = 6 cm on the page; 5 m = 500 cm, 500 ÷ 100 = 5 cm. Sketch the plan on the board as pupils call out each scaled length. The focus is the real-to-paper arithmetic and the scale drawing, not plotting points on a grid. Watch for the common slip of dividing the metres straight away without changing to centimetres first; reconcile that aloud as it comes up.

Keep the active portion to one measurement so the minutes are realistic with a mixed-ability class. Groups of four or five, one metre stick per group. Use wherever the school has a long wall — corridor, hall, covered area, or the classroom itself. Pupils measure one real length, convert it from real to paper at 1:100, and sketch the plan. Finish with a short paper read-back in the reverse direction at the seats: given a labelled scale plan, multiply each paper length by 100 to find the real lengths. Stretch for fast finishers: a 4 cm × 3 cm rectangle at 1:25 — find the real perimeter only (length scales by the ratio; do not ask for area, which scales differently). Watch for the unit-matching slip (dividing metres without changing to centimetres) and reconcile it as you circulate.

Recap the divide-for-paper, multiply-for-real rule once more before pupils move to the activity-book page.