Where does interest on interest come from?
Reveal one year at a time. Turn repeated multiplication into a formula, and compare compound growth with simple interest.
The classroom · Think before you calculate
Small steps.
Big mathematical ideas.
Explore compound interest, percentage change and regular saving. Make a prediction, build a table, then explain the pattern. Free activities for students, with worked answers for teachers and independent learners.
Same percentage. Different change.
Investigate growing savings and a falling asset value. Explain why a 10% fall is not the same as subtracting $100 every year.
Build a savings plan, one period at a time.
Model the first four payments, investigate their timing and build a spreadsheet with visible arithmetic.
Choose your starting point
For lessons 1 and 2, you should be comfortable finding a percentage of an amount and using a calculator. For lesson 3, first practise compound growth and reading a spreadsheet cell reference.
- Write down a prediction before using the reveal buttons.
- Check each new row against the previous closing balance.
- Explain the pattern in words before writing a formula.
- Try the questions independently, then reveal the worked answers.
Want paper practice? Use the printable compound interest worksheets and reverse-interest extension.
For teachers
These are original resources designed around selected NSW mathematics outcomes, not reproductions of another provider’s lessons. Activities 1 and 2 support Stage 5 financial mathematics; activity 3 is a senior extension. Teachers should adapt the pacing and difficulty to their class.
Lessons include accessible data tables, keyboard-operated controls and printable worked content. There are no classroom accounts, student profiles or answer submissions.
Curriculum references are provided on each lesson. They describe topic alignment, not approval or endorsement by NESA or MathsLinks. The senior resource references the 2024 Standard syllabus, whose first HSC examination is in 2027.