SOLUTION: Starting at home, Christopher traveled uphill to the hardware store for 24 minutes at just 15 mph. He then traveled back home along the same path downhill at a speed of 30 mph.

Question 858788: Starting at home, Christopher traveled uphill to the hardware store for 24 minutes at just 15 mph. He then traveled back home along the same path downhill at a speed of 30 mph.
What is his average speed for the entire trip from home to the hardware store and back?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Starting at home, Christopher traveled uphill to the hardware store for 24 minutes at just 15 mph.
He then traveled back home along the same path downhill at a speed of 30 mph.
What is his average speed for the entire trip from home to the hardware store and back?
:
Let d = the one-way distance to the store
:
let a = his average speed for the round trip
:
Write a time equation, time = dist/speed
time up + time back = total time
+ =
multiply by 30a to clear the denominators, results:
2ad + ad = 30(2d)
3ad = 60d
divide both sides by d
3a = 60
a = 60/3
a = 20 mph is his average speed for the round trip
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