SubjectNest resource library

Development draft · local review needed

Day 18 · Find the missing group countYear 5 Maths · T1 W3–4 · Day 18 lesson

Prepare this lesson

Year 5 / Mathematics / Term 1 / Weeks 03 04

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

Open for this lesson: Pack guide · Sources and materials · Worked swaps · Aids and text routes.

Download full sequence

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.

Fresh learner checks

Success: solve a multiplication equation with an unknown, then check by substitution. Prepare: 24×?=720 card. Codes: AC9M5A02, AC9M5A01.

  1. Recall · 2 min. Ask what 24×10 and 24×3 are. Key: 240 and 72.
  2. Model · 5 min. 24×?=720: use inverse 720÷24=30 or note 24×3=72 then tenfold to 720. Substitute: 24×30=720. Name ? as number of equal groups in this model.
  3. Guide · 6 min. Solve ?×16=672: 16×40=640, 16×2=32, total 672, so ?=42. Check with 672÷16=42. Correct a plausible ?=4.2 by scale.
  4. Choose · 7 min. Day 18 A/B/C unknown-value route; child may use related facts, an area model, division or trial and refinement. Require a substitution check.
  5. Exit · 3 min. “Would 3 or 30 fit 24×?=720?” Key: 30; 24×3=72. Ask why the zero changes the total.
  6. Record · 2 min. Note strategy and check rather than speed or preferred symbol format.

Source: https://neuroforge.io/subjectnest/library/resources/year-5/mathematics/term-1/weeks-03-04/day-18 · Original material © NeuroForgeIO Pty Ltd 2026 · CC BY 4.0: https://creativecommons.org/licenses/by/4.0/ · Credit the source and note changes. External sources keep their own terms.