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Year 8 Maths — Compound interest

Work out compound interest and the amount it grows to, and use the same idea for growth and depreciation.

Name: ________________________

  1. 1.A machine worth $20000 loses 10 per cent of its value every year. What is it worth after 2 years? Give just the number.

  2. 2.$8000 is invested at 5 per cent per year, compounded yearly, for 2 years. What amount does it grow to? Give just the number.

  3. 3.$4000 is lent at 10 per cent per year, compounded half-yearly, for 1 year. What amount is owed at the end? Give just the number.

  4. 4.A town of 10000 people grows by 10 per cent every year. How many people live there after 2 years?

  5. 5.The simple interest on $4000 at 10 per cent for 2 years is $800. What is the compound interest on the same sum at the same rate and time? Give just the number.

  6. 6.$1000 is invested at 10 per cent per year, compounded yearly. Match each length of time to the amount it grows to.

    • 1 year
    • 2 years
    • 3 years
    • 4 years
    • 5 years
    • $1100
    • $1610.51
    • $1464.10
    • $1210
    • $1331

  7. 7.$2000 is invested at 10 per cent per year, compounded yearly, for 3 years. What amount does it grow to? Give just the number.

  8. 8.Each card is a rate at which $1000 is invested for 2 years, compounded yearly. Put them in order by the amount at the end, smallest first.

    • 8 per cent per year
    • 20 per cent per year
    • 15 per cent per year
    • 10 per cent per year
    • 5 per cent per year

Answer key — Year 8 Maths — Compound interest

  1. 1. 16200
  2. 2. 8820
  3. 3. 4410
  4. 4. 12100
  5. 5. 840
  6. 6. 1 year → $1100; 2 years → $1210; 3 years → $1331; 4 years → $1464.10; 5 years → $1610.51
  7. 7. 2662
  8. 8. 1. 5 per cent per year 2. 8 per cent per year 3. 10 per cent per year 4. 15 per cent per year 5. 20 per cent per year