SOLUTION: A train goes from boston to new york averaging 40 km per hour and returns averaging 60 km per hour. what is the average speed for the round trip?

Question 425343: A train goes from boston to new york averaging 40 km per hour and returns averaging 60 km per hour. what is the average speed for the round trip?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A train goes from boston to new york averaging 40 km per hour and returns averaging 60 km per hour. what is the average speed for the round trip?
:
Let a = speed for the whole trip
let d = the one way distance
:
Write a time equation, Time = dist/speed
from time + to time = total time
+ =
Multiply by 120a, results
3ad + 2ad = 120(2d)
5ad = 240d
Divide both sides by d
5a = 240
a =
a = 48 km/hr is the av for the round trip
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