Answer:
The average speed is 41.3 mph.
Step-by-step explanation:
I complete the travel in 4 sections.
In the first section I travelled: 20 m/h . 0.5 h = 10 m
In the second section I travelled: 40 m/h . 1 h = 40 m
In the third section I travelled: 30 m/h . 0.5 h = 15 m
In the fourth section I travelled: 50 m/h . 0.5 h = 100 m
In total I travelled 165 meters.
d = 10 m + 40 m + 15 m + 100 m = 165 m
The time used to do this travel was 4 hours.
t = 0.5 h + 1 h +0.5 h + 2 h = 4 h
The average speed is s = d / t = 165 m / 4 h = 41.25 m/ h ≅ 41.3 mph