SOLUTION: how can i calculate average speed when a plane is flying from one city to another and is 550 miles per hour and is 430 miles per hour on the return flight.

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Question 465940: how can i calculate average speed
when a plane is flying from one city to another and is 550 miles per hour and is 430 miles per hour on the return flight.

Found 2 solutions by ankor@dixie-net.com, Alan3354:
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
calculate average speed when a plane is flying from one city to another and
is 550 miles per hour and is 430 miles per hour on the return flight.
:
Let a = the average speed for the round trip
Let d = the one-way dist
:
Write a time equation: time = dist/speed
:
outbound time + return time = total time
d%2F550 + d%2F430 = %282d%29%2Fa
Actually we don't need d, just put it in here to illustrate what we are doing here
Divide thru by d, and we have:
1%2F550 + 1%2F430 = 2%2Fa
Multiply by 23650a to clear the denominators, results
43a + 55a = 47300
98a = 47300
a = 47300%2F98
a = 482.653 mph is the average speed
:
:
You can confirm this solution by choosing a value for d and finding the total of the actual times.

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
how can i calculate average speed
when a plane is flying from one city to another and is 550 miles per hour and is 430 miles per hour on the return flight.
---------------
Average speed for a round trip is similar to parallel resistors, but times 2.
Avg speed = 2*550*430/(550 + 430)
= 473000/980
=~ 482.65 mph
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It's always less than the average of the 2 speeds, because more time is spent moving at the lower speed (unless they're the same speed).