Roy is hiking down a mountain at an average rate of 3 miles per hour. He wants to know how far he can hike in a given number of hours. Which is the dependent variable in this problem situation?
A. time
B. distance
C. altitude
D. speed

To convert a distance between miles and feet, you can use the equation f = 5280m, where f represents the number of feet and m represents the number of miles. In this equation, which describes the role of f ?

A. the dependent variable

B. the independent variable

C. the dependent quantity

D. the independent quantity

You bought books from an online book store that charges a flat fee for shipping each order. There was no sales tax on this purchase. The graph shows the cost of purchasing x books. About how much did the books cost if the total purchase was $31.50?

A. $3.50

B. $7.00

C. $28.00

D. $31.50