Question 265895
for the first and last half hour it travels 300mph

so since first half hour and last half hour together account for one hour

the distance traveled is 300 miles

remaining distance is 5700-300=5400 miles

now it travels this distance at 600mph

so time taken is 5400/600 = 9 hours

so first half hour it travels 150 miles      (at 300mph)
then for 9 hours it travels 5400 miles       (at 600mph)
then the last half hour it travels 150 miles (at 300mph)

so total time is 0.5+9+0.5=10 hours

so total time taken to travel 5700 miles is 10 hours