Question 314471
Let the distance between A and B is 40 Km.
Hence, Total distance covered in journey=40+40=80 Km
Average Speed = 50 Km/hr

Therefore, avg time required for the totaltrip= 80/50= 1 3/5 Hrs
As 1 hr is aleady used during onward journey, remaining time for return journey is 1 3/5 -1 = 3/5 Hrs.for travelling back 40 Kms from B to A.

Hence, Speed = 40 / (3/5)=200/3=66.66 Km/Hr   [ Ans(D)]