A moving body travels distance d at uniform speed V1, and travel distance d at uniform speed V2 prove that its average speed is 2V1*V2/V1 + V2

Use the average speed formula.



The distance now, is 2d.

The time, t_1 for the first part of the journey is given by

That for the second part is given by

Sub in your equation;



Now you can simplify :)

[Thanks ebaines for the other one ;)]