SOLUTION: What is the average rate, in miles per hour, of a car that travels 20 miles at 40 miles per hour and then 10 miles at 60 miles per hour? I also need a formula to along with this

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Question 821094: What is the average rate, in miles per hour, of a car that travels 20 miles at 40 miles per hour and then 10 miles at 60 miles per hour?
I also need a formula to along with this. Thank you!
Answer by TimothyLamb(4379) About Me  (Show Source):
You can put this solution on YOUR website!
time per leg:
t = d / s
t = 20/40 + 10/60
t = 1/2 + 1/6
t = 6/12 + 2/12
t = 8/12
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avg speed:
s = d / t
s = (20 + 10)/(8/12)
s = (30)/(8/12)
s = 45 mph
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NOTE:
avg speed is NOT: (40+60)/2=50
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