Answer:
25 mph
Explanation:
For the first 15 minutes, his speed is 40 mph. The distance he travels is:
d = (40 m/h) (15 min) (1 h / 60 min)
d = 10 miles
He then stops for 25 minutes.
He completes the journey at 45 mph. The whole trip takes 1 hour, so the time he drives at this new speed is 60 − 25 − 15 = 20 minutes. The additional distance he travels is:
d = (45 m/h) (20 min) (1 h / 60 min)
d = 15 miles
The total distance is 25 miles, and the total time is 1 hour. His average speed is therefore:
r = 25 mi / 1 h
r = 25 mph
Graph:
desmos.com/calculator/lthu2yiiyp