Answer:
60 mph
Explanation:
Given;
Total distance covered d = 440 miles
Average speed in the first 4 hours v1 = 50 mph
Total time taken for the whole trip t = 8:00 to 4:00pm
t = 16:00-8:00 = 8 hours
Firstly we need to calculate the distance covered during the first 4 hours;
d1 = average speed × time = v1 × t1
t1 = 4
d1 = 50 × 4 = 200 miles
Then we need to calculate the distance covered in the second period of the journey;
d = d1 + d2
d2 = d - d1
Substituting the values;
d2 = 440 - 200
d2 = 240 miles
The time taken for the second period of travel t2;
t2 = t -t1 = 8-4
t2 = 4 hours
Average speed = distance travelled ÷ time taken
The average speed for the second part of the trip v2 is;
v2 = d2 ÷ t2
Substituting t2 and d2;
v2 = 240 miles ÷ 4 hours
v2 = 60 mph
The average speed during the second part of the trip is 60 mph