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 1700 miles, for a total gas consumption of 55 gallons. How many gallons were consumed by each of the two cars that week?

Answer 1

answer(s):

car one consumes 30 gallons of gas.
care two consumes 20 gallons of gas.


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.