Write the four numbers on the IWB with space after the last one. Take three hands-up answers, not open call-outs. Listen for pupils saying 'it goes up by three' — that's the seed for the lesson.

Don't confirm an answer yet. Park their predictions on the board so we can come back to them in Watch and Notice.

What to point at on each machine

• Add 3 — say each input-output pair aloud: 'two in, five out — five in, eight out — eight in, eleven out'. The class will hear the +3 in the rhythm.
• Multiply by 2 — pause on the gap between 4 and 8: 'the jumps get bigger because we double what we already had'.
• Subtract 5 — point out the rule still works when numbers go down, not just up.
• Double then add 1 — slow down on this one. Say it as 'one doubled is two, plus one is three', then 'three doubled is six, plus one is seven'. Two things every time.

Lock-in: before moving on, the class should be able to say what is hiding in each machine in one short sentence.

This round is for talking it through together — pupils take turns at the board and the class agrees or corrects out loud. We stay on the +3 rule for the whole step so pupils get sustained practice with the chain-the-output idea.

Call a pupil up, ask them to enter 2, and ask the class 'what will come out?' Wait for a chorus before tapping Send through. Then feed 5 back in. Then 8. The class should be able to call 11, 14, 17 before the machine confirms.

Then a second pupil comes up and starts a fresh sequence from 7. Same rule, different start: 7, 10, 13, 16, 19. Pupils should notice the rule does the same thing every time, no matter where we start.

• Watch for pupils who add the gap (5 − 2 = 3) to the last term instead of applying the rule to the last output. For +3 the answer happens to match either way; the difference will matter in Class Challenge when rules become ×4, ×5, double-then-add-1. Revoice each time: 'we take what came out and put it back in'.
• If a prediction is wrong, don't correct it yourself — let the machine reveal, then ask the pupil what they think happened.
• The other rules from Watch and Notice (×2, −5, double then add 1) come back in Class Challenge as hidden rules — don't try to swap the live machine here.

This round is the practice bank — pupils take turns at the board, check each answer, and the class confirms before moving on.

The five rules the interactive cycles through are +3, ×4, +7, ×5, and the stretch double then add 1. The extension bank holds three more two-step rules (×6; ×3 then −2; ×2 then +3) and the homework bank has +4, ×3, −6, +10, and a two-step ×2 then +1 for at-home practice. The last challenge in the main bank is genuinely harder — single-rule guesses won't fit. Listen for pupils saying 'it's not just times two, because two should give four, but two gives five' — that's the moment two operations click.

• If pupils are stuck, prompt them to try an input the machine hasn't shown yet — that's the whole point of probing.
• Always reveal the rule before moving on, even if the class got it. The reveal is the confirmation.
• Two and a half minutes per challenge is the budget — if a challenge clicks fast, move on; if the stretch needs the extra time, take it from one of the earlier ones.