6.5 Growth, decay and repeated percentage change — Practise

Work independently. Questions and answers below come from checked practice records.

1. A population of 2400 grows by 3% each year for 4 years. Work out the population, to the nearest whole person.
2. A machine worth £8000 loses 12% of its value each year. Work out its value after 3 years.
3. A quantity starts at 500 and increases by 8%, then by 6%. Work out the final quantity.
4. A value is multiplied by 0.72. State the percentage decrease.
5. A £4000 investment grows to £4410 in 2 years with annual compound growth. Find the annual percentage rate.
6. A car worth £18 000 depreciates by 18% each year. Work out its value after 2 years.
7. A £1000 amount grows by 10% then falls by 10%. Work out the final amount and compare it with £1000.
8. A population of 5000 grows by 2% each year. Work out its population after 10 years, to the nearest whole person.
9. An investment doubles in 12 years with annual compound growth. Find the annual multiplier to 3 significant figures.
10. A substance decays by 7% each hour. What percentage remains after 5 hours?