SOLUTION: A motorist travels 90 miles at a rate of 20 miles per hour. If he returns the same distance at an average rate of 40 miles per hour, what is his average speed for the entire trip,

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Question 359367: A motorist travels 90 miles at a rate of 20 miles per hour. If he returns the same distance at an average rate of 40 miles per hour, what is his average speed for the entire trip, in miles per hour?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A motorist travels 90 miles at a rate of 20 miles per hour.
If he returns the same distance at an average rate of 40 miles per hour,
what is his average speed for the entire trip, in miles per hour?
:
Let a = average speed for the trip
:
Write a time equation, time = dist/speed
:
Go time + return time = total time
90%2F20 + 90%2F40 = 180%2Fa
:
Multiply by 40a to clear the denominators, then solve for a