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Day 9 · Pick a method and defend itYear 11 Specialist Maths · T1 W1–2 · Day 9 lesson

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Year 11 / Specialist Mathematics / Term 1 / Weeks 01 02

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

Open for this lesson: Pack guide · Practice cases · Daily routes · Worked swaps · Fresh learner checks · Aids and text routes.

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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.

Learner prompts

Target: classify whether a new counting story needs inclusion–exclusion, disjoint addition, multiplication, or a branch combination, and justify the classification. Prepare: A/D/E/F, method chooser.

  1. Launch · 2 min. Put both, one of, one from each and branch then pair on cards. Ask which phrase hints at duplicate counting.
  2. Model · 4 min. A overlaps → inclusion–exclusion 25. D one disjoint session → addition 7. E two stages → multiplication 12. F exclusive routes with stages inside → 2×3+2×2=10.
  3. Guided reading · 5 min. Ask what assumption each calculation requires and what a wrong operation would count instead. A needs pair overlap 5; E needs every shape-caption pairing.
  4. Practice route · 7 min. Choose Day 9 route; sort four cards by method, supply one answer and one counterexample to an invalid operation.
  5. Audit · 4 min. Challenge “just look for OR/AND.” Learner states the real test: mutually exclusive outcomes, overlapping sets, or stages that jointly form an outcome.
  6. Exit · 3 min. “Can the same surface word OR always justify plain addition?” Expected: no; A's overlapping OR needs inclusion–exclusion.

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