Question

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 20 miles per gallon of gas. During one particular week, the two cars went a combined total of 2000 miles, for a total gas consumption of 70 gallons. How many gallons were consumed by each of the two cars that week?

Answer 1

Explanation:

Let x = gallons consumed by car 1

Let y = gallons consumed by car 2

We set up our equations:

35x+40y = 1850 eq1

x+y = 50 eq2

Substituting eq 2 into eq 1,

35x+40(50-x) = 1850

35x+2000-40x = 1850

-5x+2000 = 1850

-5x = -150

x = 30

Substitute value of x into eq 2.

x+y = 50

30+y = 50

y = 20

Car 1 consumes 30 gallons of gas.

Car 2 consumes 20 gallons of gas.