A jet airliner flies at 300 mph for the first half hour and

A jet airliner flies at 300 mph for the first half hour and last half hour of a flight. The rest of the time it flies at 600 mph. How long does it take to fly a distance of 5700 miles?
time of flight= _____ hours

Solution

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