Take three hands-up estimates, not open call-outs. Don't correct any of them yet — the point is to get pupils anchored on the idea that both the oats and the water have to grow. Listen for anyone who says only the oats need to change; that's the misconception this lesson targets.

Pancakes for 4 is the baseline: 2 cups flour, 3 eggs.

For 8, ask before revealing: crowd doubles, so what happens to the flour? Scale factor ×2, reveal 4 cups flour and 6 eggs.

For 12: 12 is three times 4, so ×3. Reveal 6 cups flour and 9 eggs. Land it here that both bars keep the same shape, just three times longer.

Soda bread baseline is a 500 g loaf, 5 parts flour to 1 buttermilk.

For the 1,500 g loaf: 1,500 ÷ 500 = ×3, so every part triples to 15 parts flour and 3 buttermilk.

Draw out that the rule holds whatever the unit — cups, eggs or grams: proportion multiplies everything by the same factor.

This round is for talking it through together — pupils take turns at the board while the whole class predicts both amounts aloud before each reveal, then agrees or corrects.

Name the scale factor before touching the bars each time: 4 people is ×2, 6 people is ×3, 14 people is ×7. Have a pupil at the board grow both bars, and the class calls out both scaled amounts. The wrinkle to watch for is that the ×7 step is the key one — pupils see the same rule cope with an awkward factor. If anyone scales only the oats, stop and ask what happens to the taste if the water stays the same?

These are the practice questions — pupils take turns at the board, check each answer, and the class confirms before moving on. Keep the board work brisk rather than over-explaining.

For every problem, have the class find the scale factor first (18 ÷ 6 = ×3; 6 ÷ 2 = ×3; 8 ÷ 2 = ×4). Then both quantities grow by that factor. The journey problem is the ceiling — pupils must spot that 8 litres is four times 2 litres, so the distance is four times 30 km, which is 120 km; the stretch, 10 litres, is ×5, so 150 km. Watch for pupils who add instead of multiply (they may say 30 + 30 = 60 for double the fuel, which is fine for ×2 but breaks at ×4).

On the chairs and journey problems the two bars will look very different in length (e.g. helpers beside chairs, litres beside kilometres). That is expected — tell the class the point here is the scale factor, not the bar shape, so they are not thrown by the mismatched bar lengths.