Percentages: แบบฝึกหัด

A library has a total of \( 1,200 \) books. If \( 45\% \) of the books are classified as fiction, how many fiction books are in the library?

If \( 40\% \) of a number \( n \) is \( 24 \), what is \( 30\% \) of \( n \)?

The value of a certain stock increased by \( 20\% \) in the first year and then decreased by \( 15\% \) in the second year. What was the total percentage change in the stock's value over the two-year period?

If \( 15\% \) of \( 400 \) is equal to \( 20\% \) of a number \( x \), what is the value of \( x \)?

The price of a computer was decreased by \( 20\% \) of its original price. One month later, the new price was increased by \( 20\% \). What is the final price of the computer relative to the original price?

On a test with \( 60 \) questions, Sarah answered \( 85\% \) of the questions correctly. How many questions did she answer correctly?