SOLUTION: In a family there are two cars. The sum of the average miles per gallon obtained by the two cars in a particular week is 45. The first car has consumed 40 gallons during that week,

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: In a family there are two cars. The sum of the average miles per gallon obtained by the two cars in a particular week is 45. The first car has consumed 40 gallons during that week,      Log On


   

Question 196171: In a family there are two cars. The sum of the average miles per gallon obtained by the two cars in a particular week is 45. The first car has consumed 40 gallons during that week, and the second car has consumed 20 gallons, for a total of 1400 miles driven by the two cars combined. What was the average gas mileage obtained by each of the two cars that week?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let a= the average mpg for the 1st car
Let b= the average mpg for the 2nd car
given:
(1) a+%2B+b+=+45 mi/gal
(2) 40a+%2B+20b+=+1400 mi
Multiply both sides of (1) by 20
and subtract (1) from (2)
40a+%2B+20b+=+1400
-20a+-20b+=+-900
20a+=+500
a+=+25 mi/gal
and
(1) a+%2B+b+=+45
25+%2B+b+=+45
b+=+45+-+25
b+=+20 mi/gal
The 1st car got 25 mpg and the 2nd car got 20 mpg