SOLUTION: When Frank Gresham drove 150 miles in the city, the fuel efficiency rating for his car was 18 miles/gallon. For highway driving, the fuel efficiency rating is 24 miles/gallon. How

Question 438390: When Frank Gresham drove 150 miles in the city, the fuel efficiency rating for his car was 18 miles/gallon. For highway driving, the fuel efficiency rating is 24 miles/gallon. How far will Frank have to drive on the highway for his car to have a fuel efficiency rating of 20 miles/gallon.
My teacher gave us this problem to work on over break and he gave us the answer of 100 miles but i dont know how to get there. I checked this website and the problem has already been answered but in the explanation it says 24 - 20 is 3 which it is obviously not so i still need help setting up the problem. thank you :D
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = highway miles he has to drive
In words:
(total miles driven)/(gallons used) = efficiency in mi/gal
-------------
given:
Gallons of gas used in city =
Gallons of gas used on highway =

Multiply both sides by

He has to drive 100 miles on the highway
check answer:

OK
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