SOLUTION: When Frank Gresham drove 150 miles in the city, the fuel efficency rating for his car was 18mi/gal. For Highway driving, the fuel efficiency rating is 24 mi/gal. How far will Frank

Question 136924: When Frank Gresham drove 150 miles in the city, the fuel efficency rating for his car was 18mi/gal. For Highway driving, the fuel efficiency rating is 24 mi/gal. How far will Frank have to drive on the highway for his car to have a fuel efficency rating of 20mi/gal
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
When Frank Gresham drove 150 miles in the city, the fuel efficiency rating for his car was 18mi/gal. For Highway driving, the fuel efficiency rating is 24 mi/gal. How far will Frank have to drive on the highway for his car to have a fuel efficiency rating of 20mi/gal
:
Treat it like a mixture problem
:
Let x = no, miles required to get an efficiency rating of 20 mi/gal
:
18(150) + 24x = 20(x+150)
:
2700 + 24x = 20x + 3000
:
24x - 20x = 3000 - 2700
:
3x = 300
x =
x = 100 miles
:
:
Let's see if that works
At 18 mpg: 150/18 = 8.33 gal
At 24 mpg: 100/24 = 4.17 gal
----------------------------
the total gallons = 12.5
:
Av for trip: 250/12.5 = 20 mpg; confirms our solution
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