SOLUTION: Genny travels from one elementary school to another and back at a rate of 20 miles per hour one way and 30 miles per hour another way. What is her average rate of speed for both t

Question 930733: Genny travels from one elementary school to another and back at a rate of 20 miles per hour one way and 30 miles per hour another way. What is her average rate of speed for both trips?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Genny travels from one elementary school to another and back at a rate of 20 miles per hour one way and 30 miles per hour another way.
What is her average rate of speed for both trips?
:
let d = the one way distance of the trip
let a = the average speed for the round trip
:
Write a time equation; time = dist/speed
to time + return time = total time
+ =
multiply equation by 60a; cancel the denominators
3ad + 2ad = 60(2d)
5ad = 120d
divide both sides by d
5a = 120
a = 120/5
a = 24 mph is the average for the round trip

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