Examining Applied Rational Functions

Rational functions occur in amazing places. They even occur in the area of comparing the fuel costs for automobiles. Some people place great importance on increased fuel efficiency and the resultant reduced fuel costs. Just how much money is saved by improved gas mileage? For example if gasoline costs $1.00 per gallon and you drive 15,000 miles per year, how much would you save by improving gas mileage from 10 mpg to 20 mpg?