numerical

Average speed is given by = total distance covered/ total time taken

 

Let the object covers a total distance S

Then time taken to cover first half of the distance = S/2u

&, time taken to cover first half of the distance = S/2v

 

Therefore average speed is given by Vavg.= S/(S/2u + S/2v)

Vavg. = 1/[(u+v)/2uv]

i.e., Vavg. = 2uv/u+v

 

Hope this helps.