SOLUTION: A certain car that is being tested by its manufacturer uses its entire fuel supply in about 38 hours when idling. The same car, when driven at 60 miles per hour on a test track, u

Question 356170: A certain car that is being tested by its manufacturer uses its entire fuel supply in about 38 hours when idling. The same car, when driven at 60 miles per hour on a test track, uses about three-and-a-half times as much fuel per hour as it does when idling. If the engine has been idling for 10 hours and the car is then run at 60 miles per hour, how much longer will the car run before it uses up all of its fuel (assuming it started with a full tank)?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
A certain car that is being tested by its manufacturer uses its entire fuel supply in about 38 hours when idling. The same car, when driven at 60 miles per hour on a test track, uses about three-and-a-half times as much fuel per hour as it does when idling. If the engine has been idling for 10 hours and the car is then run at 60 miles per hour, how much longer will the car run before it uses up all of its fuel (assuming it started with a full tank)?
...
let x liters be the capacity of the tank
when idling it uses x/38 of the fuel / hour
...
at 60 mph it uses 3.5 times that of idling
3.5 *x/38
7/2*x/38
=7x/76 per hour will be the fuel consumption
...
10 hours idling consumption = 10x/38
Balance fuel will be x - 10x/38
=(38x-10x)/38
=28x/38
...
quantity of fuel/consumption per hour at 60 mph = number of hours
(28x/38) / (7x/76) = hours
28x/38 *76/7x
= 8 hours
it can run for 8 hours
...
m.ananth@hotmail.ca
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