Answer :

AL2006
Average speed = (total distance) / (total time)

Average speed = (192 km) / (8 hours) = 24 km per hour .
Time for round trip = 8 hours

thus, time for trip = 8/2 = 4 hours.

Speed = distance / time

= 96/4 = 24 km/h

Thus, his average speed was 24 km/h