Question

A family has two cars. The first car has a fuel efficiency of 30 miles per gallon of gas and the second has a fuel efficiency of 40 miles per gallon of gas. During one particular week, the two cars went a combined total of 1800 miles, for a total gas consumption of 50 gallons. How many gallons were consumed by each of the two cars that week?

Answer 1

30x+40(50-x)=1800
Solve for x
X=20 for the first car

50-20=30 for the second car

Answer 2

One car 40 miles /gallon
other car 30 miles/gallon
..
Total miles = 165
gas used = 45 gallons
...
let first car drive x miles
second car drive y miles
..
x/40 + y/30 = 45
(30x+40y)/30*40 = 45
30x+40y = 45*40*30
30x+40y=54,000