Answer:
The average speed ever the entire trip was 3.9 m/s.
Explanation:
We can calculate the average speed of the person over the full trip as:
s = (4.9 m/s + 2.9 m/s) / 2 = 3.9 m/s
To calculate the average speed we don't need what is the total displacement, but only the speed in each section of the trip (4.9 m/s and 2.9 m/s) and the number of sections of the trip (2 sections).