Year level: 4

Strand: Number, Algebra

Lesson length: 60 mins

In this second of three lessons, students use mathematical modelling to solve problems that involve financial decisions.

They will be guided to use the 4-step problem solving model to support them to unpack the problem, generate a plan to help solve it, and check their ability to work mathematically.

Students will explore different ways to estimate and form possible solutions to the total earnings over a period of time. The lesson allows students to be creative in the way they infer the stated problem and select strategies to find possible solutions.

They will communicate their thinking and justify their approach to the problem and their solutions.

### Achievement standard

Students use their proficiency with addition and multiplication facts to add and subtract, multiply and divide numbers efficiently. They use mathematical modelling to solve financial and other practical problems, formulating the problem using number sentences, solving the problem, choosing efficient strategies and interpreting results in terms of the situation.

### Content descriptions

Students use mathematical modelling to solve practical problems involving additive and multiplicative situations including financial contexts; formulate the problems using number sentences and choose efficient calculation strategies, using digital tools where appropriate; interpret and communicate solutions in terms of the situation. AC9M4N08

Students develop efficient strategies and use appropriate digital tools for solving problems involving addition and subtraction, and multiplication and division where there is no remainder. AC9M4N06

Recall and demonstrate proficiency with multiplication facts up to 10 x 10 and related division facts; extend and apply facts to develop efficient mental strategies for computation with larger numbers without a calculator. AC9M4A02

### General capabilities

Numeracy

Critical and Creative Thinking

• Analysing (Interpret concepts and problems Inquiring)
• Inquiring (Identify, Process and Evaluate information)

Students respond to one of the questions: Why is it important to know how to calculate multiple money amounts? How could you use this learning in your current lives? How might it be useful for you in future years?

Formative assessment

• Observe the working out in students' workbooks while they are developing a plan or solving the problem and make notes on your observations.
• Listen to students discussing their strategy choices with each other. Provide feedback on student’s strategies to support them to refine their ideas where necessary.
• Be familiar with the concept of pocket money.
• Estimation and approaches to make an estimate.
• Share dollar amounts in different ways.
• Follow steps to problem-solving and know problem-solving strategies they could use to find solutions.
• Adopt a growth mindset and persist through a problem for which they do not have an immediate solution.

Some students may:

• find it a challenge to read and understand the problem: there is choice in the way the money can be distributed if students elect to allocate a different value to the jobs performed. (The problem doesn’t state that the jobs are all of equal value)
• require support to move their thinking from additive to multiplicative thinking when calculating costs for a four-week period (repeated addition to multiplication)
• require support to shift their thinking when using estimation from wanting to calculate an exact value to using strategies to estimate an approximate value
• require support and encouragement to move from inefficient to efficient strategies.