Percentages：练习题

Sarah invests \( \$5000 \) in a bank account that pays compound interest at a rate of \( 3\% \) per year. Calculate the total amount of money Sarah will have in her account after 4 years, correct to the nearest dollar.

A rare painting increases in value by \( r\% \) each year.
Given that the value of the painting doubles in exactly 10 years, calculate the value of \( r \) correct to 1 decimal place.

An investor places \( \$800 \) in a savings account that pays simple interest at a rate of \( 4.5\% \) per year.
Find the total interest earned after 6 years.

The population of a town decreases at a rate of \( 4\% \) per year.
If the initial population is 25,000, find the population after 3 years, correct to the nearest whole number.

A camera is sold for \( \$425 \) after a discount of \( 15\% \) has been applied to its original price.
What was the original price of the camera?

Calculate 25% of 180 kg.

In a sale, a shop reduces all prices by \( 20\% \).
The sale price of a coat is \( \$112 \).
Calculate the original price of the coat.

A house increases in value by \( 10\% \) in the first year and then decreases in value by \( 5\% \) in the second year.
Calculate the overall percentage increase in the value of the house over the two years.

Liam invested $$1200\$ in a savings account. The account pays compound interest at a rate of \( r\% \) per year.

(a) After 3 years, the value of the investment was $$1348.32$. Calculate the value of \( r \), giving your answer to one decimal place.

(b) Liam withdrew the full amount of $$1348.32$ from the savings account and used it to buy a bicycle during a sale. The sale price of the bicycle was \( 16\% \) less than the original price. Calculate the original price of the bicycle, giving your answer to the nearest dollar.