A person is traveling to Chicago She is going 40 mph on the

A person is traveling to Chicago. She is going 40 mph on the way to Chicago and 80 mph on the way back. What is the average traveling time.

d = distance one-way
d = rt
t = d/r
Total time = d/40 + d/80 = 3d/80
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Avg r = 2d/t = 2d/(3d/80) = 160/3 mph