- #1
onemic
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Homework Statement
A locomotive travels on a straight track at a constant speed of 40 mi/h, then reverses direction and returns to its starting point, traveling at a constant speed of 60 mi/h. What is the average speed for the round-trip?
Homework Equations
avgS = distance/time
t = d/40
The Attempt at a Solution
avgS = 2d/(t+40/60(t))
= 2d/(t+(2/3)t)
= 2(t/40)/(t+(2/3)t)
= (t/20)/(t+(2/3)t)
I don't really know what to do after this point. The solution manual has the steps for the solution as:
avgS = 2d/(t+(2/3)t)
= 80t/(t+(2/3)t) = 48 mi/h
I have no idea how they got to the last step. Any help is greatly appreciated.