Take three hands-up answers, not open call-outs. Write each suggested rule on the board exactly as the pupil says it ('plus three', 'goes up by three', 'add three each time') so the class can compare the wording later.

Add 3: 4, 7, 10, 13. Settle on one agreed wording, steer to start at 4, then add 3 each time. A rule needs both the starting number and the move.

Take 5: 50, 45, 40, 35. Ask what single word changed. Only the verb: add becomes take or subtract. Name it.

Double: separate inputs, each doubling on its own, not a self-feeding chain. 1 to 2, 2 to 4, 4 to 8, 8 to 16. Ask what word works when adding a fixed amount fails. Head off add 1 then 2 then 4; revoice as each one doubles, one move not a growing list.

Double then add 1: give this the most time. 1, 3, 7, 15. Feed each output back in: 1 doubles to 2, add 1 makes 3; 3 doubles to 6, add 1 makes 7. Then show wrong order: start at 1, add 1 makes 2, double makes 4, not 3. So order is part of the rule.

This round is for talking it through together — pupils take turns at the board and the class agrees or corrects out loud. This machine shows one rule (add 3), so the work is in the wording, not in swapping rules.

Send a number through, then ask the class for the rule in words before sending the next. Hold them to a wording another person could actually use: 'add 3' is fine, 'it gets bigger' is not (bigger by how much?). Keep the watching class with it by turning to a different pupil each time — turn-and-name rather than always the same hands — and revoice the strongest answer back word for word.

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 each machine, get the rule in words first, then predict, then Check. When a wrong wording survives a single pair, ask for an input it would get wrong — that is the test that catches a poor rule. The last two are two-step rules: hold the class to naming both jobs and the order (multiply first, then add), not just one verb. Frame the final machine openly as a stretch, so a pupil who needs two or three tries feels they are doing the task right, not falling behind. Use the six-word line only as an optional extra for those who crack it.

Close by reading back two or three of the class's best-worded rules from today as the standard to aim for.