Sommer wants to buy a new car. She currently drives a car that gets 24 miles per gallon. She is contemplating buying a car that gets 40 miles per gallon. Sommer drives 15,000 miles per year. Assume that gas costs $3.85 per gallon the entire year. How much will Sommer save on gas in 1 year if she buys the new car?

answer

$962.50

set up equation

first, we want to find out how many gallons of gas she'll save a year

x1 = gallons for old car

x2 = gallons for new car

gallons saved = x1 - x2 since she uses more gallons with the old car with a lower miles per gallon

then, find how much she saves on gas by multiply the price per gallon (3.85) by gallons saved

price saved = gallons saved * price

price saved = (x1 - x2) * 3.85

gallons with old car

to find the number of gallons, we divide the number of miles (15000) by miles per gallon (24 for the old car)

x1 = 15000 / 24

x1 = 625

gallons with new car

use the same process as with the old car, but with 40 miles per gallon instead

x2 = 15000 / 40

x2 = 375

plug in values

price saved = (x1 - x2) * 3.85

price saved = (625 - 375) * 3.85

price saved = 250 * 3.85

price saved = $962.50