Answer:
Probably 128 km/h, but maybe 98.5 km/h. See below.
Explanation:
What does "at the same time" mean?
If it means that he covered the 240 km in the same time as he convered the 80 km, then this is how you solve it:
80 km in 1.25 hour
240 km in 1.25 hour
Total distance: 80 km + 240 km = 320 km
Total time: 1.25 hour + 1.25 hour = 2.5 hour
average speed = (total distance)/(total time) = 320 km / 2.5 hour = 128 km/h
If it means he covered the 240 km in the same time he covered the 80 km plus the rest, then this is how you solve it:
80 km in 1.25 hour
240 km in 1.25 hour + 45 min = 240 km in 1.25 houir + 0.75 hour = 240 km in 2 hour
Total distance: 80 km + 240 km = 320 km
Total time: 1.25 hour + 2 hour = 3.25 hour
average speed = (total distance)/(total time) = 320 km / 3.25 hour = 98.5 km/h