Read the ribbon story aloud, then take two or three hands-up answers. Hold out for the pupils who say the question is how much ribbon is left rather than just repeating the numbers.

Work each story live on the board; don't read the answers off before pupils predict them.

• Story 1 (length, add) — the word altogether signals adding two ribbons. Ask the class to spot it before you reveal.
• Story 2 (weight, take away) — used tells us to take away. Hold out for the unit: the answer is grams, not a bare number.
• Story 3 (capacity, take away) — poured then left; ask which number we start from.
• Story 4 (capacity, the litre link) — this is the one that catches people. Before anyone calculates, ask can we take ml away from a litre yet? The litre has to become 1000 ml first, then 1000 − 400 = 600 ml left. Slow right down and write both forms of the litre side by side so the swap is visible.

Talk this one through together — pupils take turns at the board and the class agrees or corrects out loud.

For each story a pupil underlines the action word, says add or take away, then builds the number sentence. The first is a length join; the second forces the litre swap (1 litre becomes 1000 ml, then take away 500 ml); the third is a straight length take-away. Keep pushing on the unit: 35 what? cm.

This is the practice round — 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.

• Challenge 3 is the litre link: ask can we take ml away from a litre yet? before anyone answers — the litre has to become 1000 ml first, then 1000 − 650 = 350 ml.
• Challenge 4 is the same litre-link skill with bigger numbers: swap 1 litre for 1000 ml, then take away the 750 ml poured out to find 250 ml left. Let a stronger pupil lead this one while the class checks each step.