Codes: AC9M3N03, AC9M3N05, AC9M3N06. Target: choose and interpret an additive model in a fictional useful context. Set out: problem cards, drawing sheet.
- Read the situation · 2 min. “The school library has 327 sorted books and 186 still to sort. How many books are in these two groups altogether?” Explain these are invented counts, not real school records.
- Estimate and model · 5 min. Ask for an approximate total, e.g. 330 + 190 ≈ 520. Draw two parts into one whole; write
327 + 186and solve by place value: 7 + 6 = 13, 2 + 8 + 1 = 11 tens, 3 + 1 + 1 = 5 hundreds → 513 books. - Guided reasonableness · 6 min. Compare 513 with the estimate and with an incorrect 1 513. Ask what an extra thousand would mean in this situation. Check
513 − 186 = 327. - Choice problems · 7 min. Pairs pick the book problem again with a different model, or “An art room had 600 paper tiles; 275 were used. How many remain?” → 325 tiles. Require a diagram or equation, a named unit and one check. Teacher asks “Which quantity is the whole?”
- Explain to a user · 3 min. Partners trade explanations. Listener asks whether the answer counts books or tiles and why the operation matches the story.
- Brief check · 2 min. Everyone writes/says a checking equation for their choice. Focus learners give a reasoned unit and check, not an unsupported numeral.
Access: adult read-aloud so English decoding does not control maths, manipulatives, picture-free text, scribed equation, AAC operation choice. Record any calculation prompt separately.