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Day 4 — Solve, then substituteYear 8 Maths · T1 W1–2 · Day 4 lesson

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Year 8 / 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.

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.

Success: solve the equality and verify it in both formulas. (AC9M8A01, AC9M8A02)

Question · 2 min. Ask which n makes totals equal, without pointing to graph first.
Model · 4 min. Write 18+7n=10n, subtract 7n from both sides to get 18=3n.
Guided finish · 5 min. Divide by 3: n=6. Substitute: A 18+42=60, B 60.
Independent compare · 7 min. Learners choose n=5 and n=7 to show direction changes: at 5, A=$53/B=$50; at 7, A=$67/B=$70.
Method compare · 4 min. Table, graph and algebra agree on six. Ask which one best exposes the exact equality and why.
Exit · 3 min. “Is A lower at five?” Key: no, A=$53, B=$50.

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