Math New Drill (Level 1) : SNJ00-0403-L1 Average speed

I went back and forth between two places with the speed of 3 km per hour on the way and 5 km per hour back on the way. 

Find the average speed per hour of the round trip.













Answer
3.75 km/h

Solution
The distance of one way is assumed to be 15km. 

The time of going is 15/3 = 5 hours and returning is 15/5 = 3 hours. 

Therefore the average speed per hour is (15 × 2)/(5 + 3) = 3.75 km/h.