Answer:
a). Average speed = 26 km per hour
b). Average velocity = 10 km per hour
Step-by-step explanation:
a). Distance between A to B = 5 km
Distance between B to C = 4 km
Total distance traveled between A to B to C and then back to B
= 5 + 4 + 4
= 13 km
Time taken to cover this distance of 13 km =
an hour
Therefore, average speed during this trip =

= 26 km per hour
b). Average velocity =

Displacement = (Distance between A to B) + (Distance traveled between B to C) - (Distance traveled from C to B)
= 5 + 4 - 4
= 5 km towards A
Average velocity =

= 10 km per hour