First let us calculate for the total time of the travel using the formula:
time = distance / velocity
time = 90 miles / 40 mph
time = 2.25 hours
Next, we calculate for the total gallons of fuel that is theoretically required:
theoretical amount needed = 90 miles / 24 mpg
theoretical amount needed = 3.75 gallons
The difference of the actual and theoretical amount is the amount which leaked:
amount leaked = 8 gallons – 3.75 gallons
amount leaked = 4.25 gallons
Therefore the amount of gallons leaked per hour is:
amount leaked per hour = 4.25 gallons / 2.25 hours
amount leaked per hour = 1.89 gallons / hr