The average speed is 49.5 m/s.
Step-by-step explanation:
As in the first trip, John travels 300 miles in 45 mph, then the time taken to cover this distance with 45 mph speed is
Similarly, in second trip, the distance covered is 300 miles with speed of 55 mph.
Then,
So average speed can be calculated by the ratio of sum of distance covered to sum of the time taken to cover the distances.
Hence, the average speed is 49.5 m/s.