Final answer:
The trucker's average velocity is 64 km/h south.
Step-by-step explanation:
The trucker's average velocity can be calculated by dividing the displacement by the time taken.
Given that the trucker has a displacement of 16 km south and takes 0.25 hours to travel, we can use the formula:
Average velocity = Displacement / Time taken
Average velocity = 16 km / 0.25 h
Average velocity = 64 km/h south
Therefore, the trucker's average velocity is 64 km/h south.