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Day 1 — Name the variable before calculatingYear 8 Maths · T1 W1–2 · Day 1 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.

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Success: express a fixed-plus-variable cost and state a sensible domain. (AC9M8A01, AC9M8A03)

  1. Read · 2 min. Show Plan A's $18 joining cost and $7 per repair. Ask which cost changes when repairs change.
  2. Model · 4 min. Let n be repairs. Write A(n)=18+7n. The 18 is fixed, the 7 multiplies the number of repairs; n=0,1,2…, not negative or half a repair.
  3. Guided build · 5 min. Learners form B(n)=10n from Plan B's no-joining-cost card. Substitute n=2: A=$32, B=$20.
  4. Independent turn · 7 min. For n=3, learners compute A=$39, B=$30 and write what each term means. Paper, tokens, speech or keyboard accepted.
  5. Error check · 4 min. Repair 18n+7 by testing zero repairs: the incorrect expression yields $7, whereas the joining fee alone would be $18.
  6. Exit · 3 min. “What does 7 represent in A?” Key: $7 for each repair, not $7 fixed joining cost.

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