Percentage Change and Simple Interest: แบบฝึกหัด

A pair of shoes is sold for \( \$450 \) at a profit of \( 25\% \). Find the cost price of the shoes.

The number of members in a sports club increased from 80 to 116. Find the percentage increase.

The population of a small town decreased from \( 2500 \) to \( 2300 \). Find the percentage decrease in the population.

A salary of \( \$20,000 \) is increased by \( 10\% \) in the first year and then decreased by \( 10\% \) in the second year. What is the final salary?

A shop sells a toy for \( \$120 \) after a \( 20\% \) discount. What was the original price of the toy?

A worker's monthly salary was increased by \(10\%\) to \$19,800.
(a) Find the worker's original salary.
(b) If the original salary is now decreased by \(10\%\) instead of increased, what would the new salary be?