Question

a body travels 60 km per hour from point a to point B and returns with 80 km per hour find average speed and average velocity

Answer 1

Average velocity will be zero(0) as the train returned back to station A so there is no displacement (since velocity=displacement/time).
Average speed :-
Let distance(dist) between A and B=x 
Case 1(A TO B)
speed=60 kmph
dist=x
therefore, time=x/60
Case 1(B TO A)
 speed=80 kmph
dist=x
therefore, time= x/80
Since, 
average speed = total dist/total time
Therefore,
average speed= x+x
                      -----------
                     x/60+x/80
= 2x
  ------------
   4x+3x/240
= 2x
   ------------
    7x/240
=2x*240/7x (x cancels with x)
=480/7
=68.57 kmph(approx)