Year 9: justify every step
Ākonga solve with unknowns on both sides and name the property that licenses each move.
- Year 9 move: Each step named, not just performed
- Evidence it produces: A solution where every line states the operation and why it is legal
Starter (10 mins)
Think of a Number
Play a "think of a number" game. "I'm thinking of a number. I add 5, and the answer is 13. What's my number?" Students work backwards. Explain that this is what we do when we solve equations: we perform the "inverse operation".
Main Activity (25 mins)
The Equation Balancer
Introduce the idea of an equation as a balanced scale. What you do to one side, you must do to the other. Use physical balance scales with weights if available, or draw them.
Use the "Equation Balancer" handout. Students work through a series of one-step equations, showing their working by applying the inverse operation to both sides.
View HandoutPlenary (15 mins)
Create Your Own Problem
Students write their own simple word problem that can be solved with a one-step equation. They translate it into algebra and solve it. For example: "There were some birds on a wire. 5 flew away, and now there are 8 left. How many were there to start with?" (b - 5 = 8).
Students can share their problems with a partner to solve.
Media Anchor (8-10 mins)
Video anchor: Solving equations with balance logic
Use this clip as a worked-example routine before students solve one-step equations independently.
Pause and discuss: What operation must be undone first, and why?
Transfer task: Students apply one method from the clip to the first equation in the next task set.
Resources Needed
- "Equation Balancer" Handout
- Balance scales and weights (optional)
- Mini-whiteboards
Curriculum alignment
- Algebra — Knowledge: - A variable can be used to represent:an unknown number, often in formulae (e.g. s in s2)a quantity that can vary or change (e.g. y = 3x + 4; A = bh)a specific unknown value t…
- Number — Knowledge: - Finding equivalent fractions and representing fractions in their simplest form - Adding and subtracting fractions, including improper fractions and mixed numbers, and repres…
- Measurement — Knowledge: - Finding equivalent fractions and representing fractions in their simplest form - Adding and subtracting fractions, including improper fractions and mixed numbers, and repres…
- Statistics — Knowledge: - Finding equivalent fractions and representing fractions in their simplest form - Adding and subtracting fractions, including improper fractions and mixed numbers, and repres…
- Algebra — Knowledge: - Finding equivalent fractions and representing fractions in their simplest form - Adding and subtracting fractions, including improper fractions and mixed numbers, and repres…
📋 Teacher Planning Snapshot
📐 Year 9 — Justify the step, not just perform it
Year 9 is where “do the same to both sides” stops being a rule to obey and becomes something to explain. For each step ākonga write WHY the equation is still true afterwards. Extension: hand them a worked solution containing one invalid step — dividing by a variable that could be zero, or subtracting from one side only — and ask them to find it and say what it broke.
Ngā Whāinga Ako — Learning Intentions
Students will develop algebraic thinking and pattern recognition (tātai tauira) through te ao Māori contexts, connecting mathematical reasoning to cultural and real-world problem-solving in Aotearoa.
Ngā Paearu Angitū — Success Criteria
- ✅ Students can identify, describe, and extend patterns using algebraic notation.
- ✅ Students can explain their mathematical reasoning and connect it to real-world contexts.
Differentiation & Inclusion
Scaffold support: Provide concrete materials and visual representations before moving to abstract notation. Offer entry-level tasks using number patterns, and extension challenges involving proof or generalisation for capable learners.
ELL / ESOL: Pre-teach key mathematical vocabulary (variable, expression, equation, pattern). Allow diagrams and tables as alternate representations. Bilingual glossaries recommended.
Inclusion: Neurodiverse learners benefit from structured step-by-step templates and multiple representations (visual, numeric, algebraic). Avoid time pressure on procedural tasks.
Tātai (to reckon, count, calculate) reflects the deep mathematical tradition within te ao Māori — from whakapapa genealogy structures to wharenui proportional geometry, navigation, and seasonal calendars. Mātauranga Māori holds rich pattern-based thinking: tukutuku panel sequences, kōwhaiwhai scroll patterns, and fishing seasonal cycles all encode algebraic relationships. Algebra taught through these lenses makes abstract thinking visible and culturally grounded.