Question 967601

A family has two cars. The first car has a fuel efficiency of 40 miles per gallon of gas and the second has a fuel efficiency of 15 miles per gallon of gas. During one particular week, the two cars went a combined total of 1425 miles, for a total gas consumption of 45 gallons. How many gallons were consumed by each of the two cars that week?
<pre>Let number of gallons used by 1st car (40 mpg), be F
Then number of gallons used by 2nd car (15 mpg) is: 45 - F
We then get: 40F + 15(45 - F) = 1,425
40F + 675 - 15F = 1,425
40F - 15F = 1,425 - 675
25F = 750
F, or number of gallons used by 1st car (40 mpg) = {{{750/25}}}, or {{{highlight_green(30)}}}
Number of gallons used by 2nd car (15 mpg) = 45 - 30, or {{{highlight_green(15)}}}