Take three hands-up answers, not open call-outs. Don't resolve the start question yet — let the disagreement sit. The 'start from the units' rule is the key one of the next step, so resist confirming it here.

4,738 + 2,569 = 7,307. Units: 8 and 9 make 17 — write 7, carry 1. Only one digit fits in a column, so the spare ten moves left because ten units are worth one ten. Three regroups here; get pupils to name each one.

Show why it moves left: lay out 17 unit cubes, trade ten for one ten-rod, slide it into the tens column — the carry-1 is that trade written down. No blocks: draw ten dots, ring them, move the ring one column left.

Between examples one and two, turn-and-name: one pupil says where the carry went and why, then revoice it for the whole room.

9,876 + 1,234 = 11,110. The real cascade — a carry lands in a full column and tips over, pushing another carry left, until a new ten-thousands digit appears. Ask how many carries they counted before revealing.

5,000 + 4,999 = 9,999. The near-miss, not a cascade — no carries, stays at four digits. The common slip is guessing ten thousand. Pause on the prediction before checking.

Drive home: a carry always moves one column left, never right, because ten in a column is worth one in the column above.

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

Step the algorithm column by column. As you reach each column, ask the class to predict the digit and the carry before it lands. Have individual pupils come up to set each column. Watch for the common slip of writing the full two-digit sum in a column instead of carrying — say the carry out loud every time: '13 — write the 3, carry the 1'. The answer is 10,803, so this one grows a fifth digit; flag that as it happens.

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.

The first sum is a quick win so every pupil enters. The next three need real working time: 9,876 + 1,234 is the cascade into a new digit, and 5,000 + 4,999 is the near-miss — let pupils predict whether it reaches ten thousand before checking. Use the on-screen Check (✓) as part of the narration: 'yes — that's it'. Fast finishers watch the board and mouth the next carry rather than working ahead.

Keep this brief. The cascade idea (one carry triggering another) is the piece worth restating, as it is the part pupils most often forget on paper.