A car completes a journey at an average speed of 40km/h. At what speed must it travel on the return journey if the average speed was 60km/h??

Question

mikey · Answer

(40+x)/2 =60.  Assuming the average for the round trip was 60km/h

anonymous · Answer

could you explain your method??

mikey · Answer

The average speed of the total trip is the sum of both the out and back times divded by two.  And you know they went 40km/h out, and that the average of the whole trip was 60. So the sum of the out trip and the unknown return trip, divided by 2 has to equal the 60km/h.

mikey · Answer

I'm assuming here that the out and back distances are the same.