SOLUTION: A student drives from home to school at an average speed of 40 km/hr and returns home at an average speed of 60 km/hr. Find the average speed for the entire trip? Why is your answe
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Question 772723: A student drives from home to school at an average speed of 40 km/hr and returns home at an average speed of 60 km/hr. Find the average speed for the entire trip? Why is your answer not 50 km/hr? Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! A student drives from home to school at an average speed of 40 km/hr and returns home at an average speed of 60 km/hr.
Find the average speed for the entire trip?
:
Let d = the one-way distance
Let a = the average speed for the round trip
:
Write time equation; time = dist/speed
:
To sch time + return time = total time + =
multiply equation by 120 a to clear the denominators, results:
3ad + 2ad = 120(2d)
5ad = 240d
divide both sides by d
5a = 240
a = 240/5
a = 48 mph is the average speed
:
Why is your answer not 50 km/hr? Because you spend more time driving 40
than you do a 60.
