SOLUTION: a car driven on a rough road on 25 kilometers per hour and on a concrete road on 70 kilometers per hour.it takes the car 5.5 hours to drive on 225 kilometers.how long does it take
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Question 531852: a car driven on a rough road on 25 kilometers per hour and on a concrete road on 70 kilometers per hour.it takes the car 5.5 hours to drive on 225 kilometers.how long does it take the car to drive on a concrete road? Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! a car driven on a rough road on 25 kilometers per hour and on a concrete road on 70 kilometers per hour.it takes the car 5.5 hours to drive on 225 kilometers.
how long does it take the car to drive on a concrete road?
:
Let t = time on a concrete road
Given the total time as 5.5 hrs, therefore
(5.5-t) = time on the rough road
;
Write a distance equation, dist = speed * time
:
Rough rd dist + smooth rd dist = 225 km
25(5.5-t) + 70t = 225
137.5 - 25t + 70t = 225
-25t + 70t = 225 - 137.5
45t = 87.5
t =
t = 1.944 hrs or 1 + .944(60) = 1 hr 57 min on the smooth road
;
:
Check this by finding the dist at each speed, (5.5-1.944=3.556)
25*3.556 = 88.89 km
70*1.944 = 136.10 km
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total km: 224.99 km
