SOLUTION: Two cyclists rode their bicycles up and down a hill. They averaged ten kilometer per hour on the way up and twenty kilometer per hour on the way down. What is their average speed f

Question 674961: Two cyclists rode their bicycles up and down a hill. They averaged ten kilometer per hour on the way up and twenty kilometer per hour on the way down. What is their average speed for the entire trip?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Two cyclists rode their bicycles up and down a hill.
They averaged ten kilometer per hour on the way up and twenty kilometer per hour on the way down.
What is their average speed for the entire trip?
:
let d = the dist up (and the dist down)
let a = average speed for the trip
:
Write a time equation, time = dist/speed
:
+ =
multiply by 20a to get rid of the denominators:
2ad + ad = 20(2d)
3ad = 40d
divide both sides by d
3a = 40
a = 40/3
a = 13 km/hr for the entire trip
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