Answer:
53.33mph
Explanation:
Let's calculated the total time spent on the journey first;
For the first 300miles the time spent is ;
From Distance = speed× time
time = Distance/ speed
= 300/60 = 5 hours
Similarly for the last 100mile the time taken is ;
100/40 = 2.5 hours
Total time spent = 5 +2.5 = 7.5 hours
Total distance covered 400miles
Therefore average speed = 400/7.5 =53.33mph