A body moves from A to B at a speed of 10 m/s and back to A along the same path at a speed of 20 m/s. Find its average speed and average velocity for the journey.
[Hint : If s is the distance covered by the body between A and B, average speed = `(2s)/(t_1 + t_2) = (2s)/[(s/v_1)+(s/v_2)} = (2v_1v_2)/(v_1 + v_2)`