One way to improve the fuel efficiency of a car is to use tires that have a lower rolling resistance—tires that roll with less resistance. Highway tests at 65 mph showed that tires with the lowest rolling resistance can improve fuel efficiency by nearly 2 mpg (miles per gallon). Consider a car that gets 35 mpg on high-rolling-resistance tires and is driven 15,000 miles per year. For a fuel cost of $3.5/gal, determine how much money will be saved per year by switching to low-rolling-resistance tires.

It will be saved $81 per year.

Explanation: A car without the tires, that gets 35mpg and is driven 15,000 miles per year, will have a fuel cost of:

1 gal ---- 35 miles

x gal ---- 15,000 miles

x =

x = 428.57 gal

Per year, 1 gal costs $3.5, then:

cost = 428.57*3.5

cost = 1500

The car with the tires, improve the efficiency in nearly 2mpg, i.e.:

efficiency = 35 + 2 = 37mpg

1 gal ----- 37 miles

y gal ----- 15,000 miles

y =

y = 405.40 gal

Per year:

cost = 405.40*3.5

cost = 1419

The difference in costs is:

d = 1500 - 1419

d = 81

With lowest rolling resistance tires, a car will save, per year, $81.