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Class 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.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.

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

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

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

  4. 4.₹8000 is invested at 5 per cent per year, compounded yearly, for 2 years. What amount does it grow to? Give just the number.

  5. 5.Find the compound interest on ₹1000 at 20 per cent per year for 2 years. Give just the number.

  6. 6.Sort each description by which kind of interest it belongs to.

    Groups: Simple interest · Compound interest

    • The amount grows faster and faster as the years go by
    • Interest is always worked out on the original sum only
    • Doubling the time doubles the interest exactly
    • A population rising by the same percentage every year
    • The interest is the same amount every year
    • Each year's interest is added on before the next year is worked out

  7. 7.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.

  8. 8.₹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
    • ₹1464.10
    • ₹1210
    • ₹1100
    • ₹1610.51
    • ₹1331

Answer key — Class 8 Maths — Compound interest

  1. 1. 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
  2. 2. 12100
  3. 3. 16200
  4. 4. 8820
  5. 5. 440
  6. 6. The interest is the same amount every year → Simple interest; Each year's interest is added on before the next year is worked out → Compound interest; Interest is always worked out on the original sum only → Simple interest; The amount grows faster and faster as the years go by → Compound interest; Doubling the time doubles the interest exactly → Simple interest; A population rising by the same percentage every year → Compound interest
  7. 7. 840
  8. 8. 1 year → ₹1100; 2 years → ₹1210; 3 years → ₹1331; 4 years → ₹1464.10; 5 years → ₹1610.51