Gas mileage actually varies slightly with the driving speed of a car (as well as with highway vs. city driving). Suppose your car averages 35 miles per gallon on the highway if your average speed is 45 miles per hour, and it averages 19 miles per gallon on the highway if your average speed is 72 miles per hour. Answer parts (a) and (b) below ...

(a) What is the driving time for a 2600 -mile trip if you drive at an average speed of 45 miles per hour? What is the driving time at 72 miles per hour?

(b) Assume a gasoline price of $3.05 per gallon. What is the gasoline cost for a 2600 -mile trip if you drive at an average speed of 45 miles per hour? What is the gasoline cost at 72 miles per hour?

a) Traveling at 45 mph, the driving time is 58 h. Traveling at 72 mph, the driving time will be 36 h.

b) Traveling at 45 mph, the gasoline cost will be $225.7.

Traveling at 72 mpg, the gasoline cost will be $417.9

Explanation:

The average speed can be calculated as the distance traveled over time:

speed = distance / time

Then:

time = distance / speed

a) If you drive at an average speed of 45 mph during a 2600-mile trip, the driving time will be:

time = 2600 mi / 45 mi/h = 58 h

If you drive at 72 mph:

time = 2600 mi / 72 mi/h = 36 h

b) For the 2600-mile trip, you will need (2600 mi * (1 gallon / 35 mi)) 74 gallons if you travel at 45 mph.

If you travel at 72 mph, you will need (2600 mi * (1 gallon / 19 mi)) 137 gallons.

Traveling at 45 mph, the gasoline cost will be (74 gallons * ($3,05/gallon)) $225.7

Traveling at 72 mph, the gasoline cost will be (137 gallons * (3.05/gallon)) $417.9