SOLUTION: A boy walked over hills at 3 kilometers per hour and on flat roads at 4 kilometers per hour. He walked 18 kilometers in five hours. How much of his trip is over hills?

Question 448365: A boy walked over hills at 3 kilometers per hour and on flat roads at 4 kilometers per hour. He walked 18 kilometers in five hours. How much of his trip is over hills?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A boy walked over hills at 3 kilometers per hour and on flat roads at 4 kilometers per hour.
He walked 18 kilometers in five hours. How much of his trip is over hills?
:
Let h = distance over hills
then
(18-h) = distance on flat roads
:
Write a time equation, time = dist/speed
:
hill time + flat time = 5 hrs
+ = 5
:
Multiply by the common denominator, 12:
12* + 12* = 12(5)
:
Cancel the denominators, results
4h + 3(18-h) = 60
4h + 54 - 3h = 60
4h - 3h = 60 - 54
h = 6 km on the hills
:
Check by finding the times (flat dist = 12 km)
6/3 + 12/4 = 5 hrs

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