Question

7. Kelsey's car has a gas tank that can hold up to 15 gallons. When the car is running, the gas burns at a constant

rate. When Kelsey first starts her car, it contains 12 gallons of gas. After three hours of having her car running,
the tank contains 8 gallons of gas.
a. At what rate is the amount of gas in the tank changing? Use a signed number, and include the unit of
measurement in your answer.
b. How many more hours will it take for the tank to empty completely? Explain or show your reasoning.

Answer 1

a) 4/3 gallons per hour

b) 6 hours

Explanation:

In 3 hours the gasoline in the gas tank drops from 12 gallons to 8 gallons
Drop in fuel level = 8 - 12 = - 4 gallons
a) SInce this drop happens in 3 hours, rate of change in gas = -4/3 gallons per hour

b) At the rate of 4/3 gallons per hour and with 8 gallons of fuel, the amount of time before the gas empties
= Fuel level/rate of change

= 8 ÷ 4/3

= 8 x 3/4

= 6 hours