Take three hands-up answers, not open call-outs. Write the actual class count on the board and read it aloud as "so many tens and so many units" — e.g. "27 is two tens and seven units". Keep this brief; the columns get built properly in the next step.

Walk each example aloud, one at a time, pointing to each column.

• 24 — say "two tens and four units"; ask which column is doing more work.
• 40 — pause before revealing; the empty units column is the key idea here — the zero is holding the place.
• 7 — emphasise that the tens column can be empty.
• 86 — read it as eight tens and six units.

This round is for talking it through together — one pupil builds at the board and the class agrees or corrects out loud.

Call a number under 100 (try 31, 56, 90, 48). Send a pupil up to build it: ten-rods into the tens column, single cubes into the units column. Ask the class "how many tens, how many units?" before they confirm. Watch for pupils who put units in the tens column — the most common slip. Rotate four pupils.

This round is the practice bank — 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 target, ask "how many tens and how many units make this number?" before the pupil checks. 30 and 80 catch out pupils who forget the empty units column; 99 is the full ceiling. Pupils not at the board watch and predict the answer — that watching is their participation.