Super basics

SubjectMathematics YearYear 9 CurriculumAC v8.4 Time135

Introduction

This set of resources provides opportunities for students to solve problems involving percentages, rates and proportions using technology (spreadsheets) in the context of superannuation. Students use the simple interest formula to work out how much interest a super account can earn over time.

This learning will lay the foundation for students connecting the compound interest formula to repeated applications of simple interest in Year 10.

Australian Curriculum or Syllabus

Achievement standard

By the end of Year 9, students solve problems involving simple interest. They interpret ratio and scale factors in similar figures. Students explain similarity of triangles. They recognise the connections between similarity and the trigonometric ratios. Students compare techniques for collecting data from primary and secondary sources. They make sense of the position of the mean and median in skewed, symmetric and bi-modal displays to describe and interpret data.

Students apply the index laws to numbers and express numbers in scientific notation. They expand binomial expressions. They find the distance between two points on the Cartesian plane and the gradient and midpoint of a line segment. They sketch linear and non-linear relations. Students calculate areas of shapes and the volume and surface area of right prisms and cylinders. They use Pythagoras’ Theorem and trigonometry to find unknown sides of right-angled triangles. Students calculate relative frequencies to estimate probabilities, list outcomes for two-step experiments and assign probabilities for those outcomes. They construct histograms and back-to-back stem-and-leaf plots.

Content descriptions

Solve problems involving simple interest (ACMNA211).

Teacher resources

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Visualiser

Visualiser

Student learning resources

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Worksheet

Suggested activity sequence

This sequence is intended as a framework to be modified and adapted by teachers to suit the needs of a class group.

Part A: What is super?

1. Use a grouping strategy to organise students in groups of 3 or 4.
2. Display and explain the information of the visualiser. Groups construct a brief definition of superannuation. Each group writes their definition on the board.
3. When all definitions are displayed, discuss the concept of super and develop a simple class definition.

Part B: Calculating super contributions

1. Explicitly teach students how to calculate the super guarantee using a gradual release of responsibility model. An example of modelling is provided below.

Super = 9.5% x salary

For example: You’re a third-year apprentice plumber and your weekly wage is \$669.53 per week. How much super should your employer pay into your super account?

Super = 9.5% x salary
= 0.095 x \$669.53
= \$63.61

2. Demonstrate a ‘working backwards’ question, for example, if your employer pays \$72.30 into your super account, what’s your salary?
3. Model to students how to use spreadsheets to solve problems. Use the visualiser on using spreadsheets if necessary. You could also refer students to Making an excel spreadsheet – Flowchart and/or Making an excel spreadsheet – How-to-sheet.
4. Students complete part 1 of the worksheet.

Part C: Calculating return on investment

1. Discuss investment returns earned on super accounts with students and the comparisons with interest. Consider the amounts people will accumulate in super if they just make contributions. Introduce the idea of interest adding to a super balance.
2. Apply the simple interest formula to some super balances to calculate return earned. Do a couple of examples on the board, for example:

Super balance \$52,460, rate 6.5% 2 years.

𝐈 = P x r x n
𝐈 = \$52,460 x .065 x 2
𝐈 = \$6,819.80

3. Students complete part 2 of the worksheet.
4. Work through solutions with the whole class.