Finding Change

Overview

In this lesson (lesson 4 of 6) students practise calculating the amount of change from a $10 note for everyday purchases, using efficient subtraction strategies and number lines.

Learning intentions

• WALT calculate change from a $10 note.
• WALT use subtraction strategies to find the difference between the amount paid and the cost.
• WALT explain how their answer makes sense using representations (number lines, diagrams, and place value reasoning).

Success criteria

• I can find the change for different transactions that start with paying $10.
• I can choose a method (counting on, compensation, or subtracting) and show my thinking.
• I can use a number line to support my calculation and check my answer.
• I can confirm whether my change is reasonable (e.g., it should be less than $10 and match the cost).

Curriculum links

• Numeracy: number and calculation using whole numbers and efficient strategies.
• Developing understanding of place value and using mental and written methods.
• Using representations to communicate mathematical thinking.
• Communicating mathematical ideas clearly for a given problem.

Lesson structure (30 minutes)

1. 3 minutes – Warm-up: “Quick Change” Students solve 2 fast teacher prompts (e.g., “$10 pay for $6.50”) and share one strategy. Teacher emphasises that change is what is left after paying for the cost.

2. 7 minutes – Mini-lesson: number line from $10 On the board, model: Cost = $4.75, Paid = $10.00. Draw a number line starting at $4.75 and count up to $10.00 (or start at $10.00 and count down by the cost). Key idea: change = difference between paid and cost. Highlight two approaches:

• Counting up from the cost to $10
• Subtracting cost from 10

3. 10 minutes – Hands-on group practice: “Money Mat” tasks Provide each group a Money Mat (printed grid or cards) with purchase prices and a fixed $10. Students work through 4–5 scenarios. For each, they:

• Write the calculation (e.g., $10.00 − cost)
• Draw a number line showing the jump(s) and landing on $10.00
• Record the change amount in dollars and cents Teacher circulates, focusing on correct difference thinking and accurate money notation.

4. 5 minutes – Whole-class check: Reasonableness talk Select 2 student solutions (one correct, one with a typical error such as subtracting the wrong way or forgetting cents). Students vote: “Does it make sense?” Prompts:

• “Where should the number line start and end?”
• “Is the change smaller than $10?”
• “Do the cents match the cost?”

5. 3 minutes – Independent exit: 2-question ticket Students complete two short transactions independently:

• Ticket A: whole dollars cost (e.g., $7.00)
• Ticket B: dollars and cents cost (e.g., $6.45) They must show either a number line or a clear subtraction strategy.

6. 2 minutes – Closure: Strategy share Students answer one question: “What strategy helped you most today?” Teacher collects tickets and notes who used number lines effectively.

Resources

• “Money Mat” (price cards and a fixed $10 starting point)
• Number line posters (marked in whole dollars and in 0.50 or 0.10 steps for cents support)
• Play money or printed coins/notes for visual learners (optional but hands-on)
• Student mini whiteboards or scrap paper for quick checking
• Exit ticket slips (2 change questions)
• Coloured pens/pencils for highlighting subtraction steps and number line jumps
• Teacher board or interactive whiteboard for modelling

Assessment

• Teacher observation during group practice: correct change calculation and correct use of difference logic.
• Formative checks: students’ number line starts/ends correctly and jumps match the cost.
• Exit ticket review: accuracy with dollars and cents, and whether reasoning is shown clearly.

Differentiation

• Support: Provide a partially completed number line template and a word bank (“Paid”, “Cost”, “Change”, “Difference”). Offer sentence starters for explaining: “I found change by… so the answer makes sense because…”
• Support (visual): Ensure each supported learner has a number line marked with 10-cent intervals and uses counting up from cost to $10.
• Extension: Give advanced students “two-step” versions where the cost is found first from given information (e.g., “I paid with $10.00 and got $2.35 change. The item was $7.65.” then swap roles).
• EAL/SEN: Use consistent language and visuals on the board; allow pointing to coins/amounts and oral explanation alongside writing. Provide extra time and a model example reprinted for reference.

Extension (optional)

• Mystery shopping scenarios: Students create their own scenario for a partner. Each scenario includes:
• A product price (cost)
• A statement that the customer paid with $10
• The missing piece is the change amount (or one part is missing for the partner to calculate)
• Partner calculates the change and explains the strategy using a number line (for visual learners) or subtraction (for those ready). Teacher checks that the scenarios always produce a valid change (less than $10 and correctly in cents).