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Day 8 — Addition can reveal a missing partYear 3 Maths · T1 W1–2 · Day 8 lesson

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Year 3 / Term 1 / Weeks 01 02 / Mathematics

Part of the full two-week lesson sequence. Check the pack guide and taught point before teaching.

Open for this lesson: Sources and materials · Check guide.

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Teacher copy: This page may include teaching prompts or answer keys. Answer keys in this public library can be viewed by anyone. Give learners a clean prompt, use checks as formative evidence, and change a case locally when prior access matters.

Codes: AC9M3A01, AC9M3N03. Target: solve □ + 185 = 432 and verify with the inverse. Set out: whole/part cards, number line.

  1. Notice · 2 min. Ask: “Which number is the whole? Is the box a part or a total?” Put 432 in the whole position.
  2. Model · 5 min. Say: “If a part and 185 make 432, I can find the missing part with 432 − 185.” Count up 185→200 (+15), 200→400 (+200), 400→432 (+32); 15 + 200 + 32 = 247. Check 247 + 185 = 432.
  3. Guided task · 6 min. Solve □ + 128 = 350 as a class → 222. Invite one child to model 350−128 and another to check 222+128. Ask what “inverse” means here: an operation can undo the other for these whole/part quantities.
  4. Choice practice · 7 min. Partners choose 276 + □ = 503 → 227, or □ − 168 = 245 → 413. Identify whether the unknown is whole or part first. Try objects, column cards or number line; record the checking sentence.
  5. Discuss trap · 3 min. Ask why 185 − 432 would not find a positive missing part for the first task. Let a learner use whole/part cards to explain.
  6. Brief check · 2 min. Everyone fills □ + 137 = 400 → 263 and shows 400 − 137 = 263 or another valid route. Focus learners explain which quantity is whole.

Access: raised whole/part cards, audible instructions, large spacing for the box, AAC labels for part, whole, check. Avoid a timed speed contest.

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