The worksheets themselves are in German – just as in class. The editor is only available in German so far.
Interest – worksheets to print
Interest: work out the interest for a year, find the capital or the rate, the interest for months and days – from class 9 on compound interest, growth factor, decrease and doubling time.
- Choose the number of tasks and the difficulty yourself
- With an answer sheet and, if you like, a QR code to the answers
- At three levels (★ to ★★★) and as group A and B
- As a single worksheet or as a task on a mixed worksheet
Interest: explained simply
If you save or borrow money, you get or pay interest. The interest is a percentage of the capital for a certain time.
How to work it out
- Interest for a year = capital · rate : 100. This is percentages: the capital is the base value, the interest is the percentage value.
- For months or days, take part of the yearly interest: · months : 12 or · days : 360. A month counts as 30 days.
An example, step by step
How much interest do €2,400 earn in a year at 3%?
- 1% of €2,400 is €24.
- 3% is 3 · €24 = €72.
- The interest for one year is €72.
Understand other variations
Capital or rate asked
€72 interest at 3%: 1% is €24, so the capital is 100 · €24 = €2,400. €72 interest on €2,400: 72 : 2,400 · 100 = 3%.
Months and days
For 4 months: €72 · 4 : 12 = €24. For 90 days: €72 · 90 : 360 = €18.
Compound interest
The interest earns interest too: €8,000 at 5% for 3 years: €8,000 · 1.05³ = €9,261. In the table you go year by year and round to the cent each year.
Growth factor
An increase of p% has the factor 1 + p/100, so 3% → 1.03. A decrease of p% has the factor 1 − p/100, so 15% → 0.85.
Decrease and doubling
A car worth €20,000 loses 15% a year: after 2 years €20,000 · 0.85² = €14,450. Doubling at 20%: 1.2³ ≈ 1.73 is not enough, 1.2⁴ ≈ 2.07 is – so after 4 years.
Your turn
How much interest do €1,500 earn at 2% in 6 months?
Show the answer and method
Yearly interest: 1% is €15, 2% is €30. For 6 months, half of it: €15.
Ready-made worksheets: Interest
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