Write 3,450 on the board and give five seconds of quiet think-time before any hands go up. Take two or three hands-up answers, not open call-outs.

Listen for pupils naming the hundreds digit as the one that changed (4 to 5). Revoice: so adding one hundred touched only the hundreds column this time. Hold the door open for the roll-over surprise coming in the next step.

3,290 + 10 lands on 3,300. First roll-over: 9 tens fill up, roll to 0, pass one into the hundreds. Two digits change, not one. Let the arc animate first, then ask: what happens if a hundred is already full?

4,950 + 100 lands on 5,050. The key one. Hundreds already at 9, roll to 0, pass one on; 4 thousands become 5. Point out the roll-over reached all the way into the thousands.

6,200 minus 1000 lands on 5,200. The calm one: only the thousands digit changes, 6 to 5, no roll-over.

2,030 minus 100 lands on 1,930. Trickiest. No hundreds to take from, so borrow; both thousands and hundreds change. The zero is where pupils slip.

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

Name the jump aloud before each pupil draws it (is this a forward jump or a back-jump?). For 4,180 + 10 the tens go 8 to 9, no roll-over. For 3,506 − 10 the tens are at 0, so both hundreds and tens change. For 2,970 + 100 the hundreds are at 9 — pause and let the class predict the roll-over into the thousands before it lands. For 7,300 + 1000 a tidy single-column change. Rotate four pupils.

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 3,950 + 100 the hundreds roll over into the thousands (4,050). 8,200 + 1000 is a clean thousands change (9,200). 4,605 − 10 has a zero in the tens, so both tens and hundreds shift (4,595). 7,040 − 100 has a zero in the hundreds, so both hundreds and thousands shift (6,940). Ask each time: does any other column have to change too?