Aplane flies at 190 mph for the first and last half hour of a flight. it flies at a higher constant speed for the rest of the flight. the route is 2090 miles. the plane is 990 miles from the destination 2 hours before the end of the flight. how many hours is the entire flight?

4.18 hours

Step-by-step explanation:

Since the plane needs 2 hours to cover the las 990 miles at the end of the flight, and in the last half hour it flies with a speed of 190mph, meaning it covers a distance of 190 / 2 = 95 miles in this last half hours.

That means for the other 1.5 hours, its cruising speed is

Beside the first and last half hour of the trip (which covers 190 miles), the cruising distance must be

d = 2090 - 190 = 1900 miles

The cruising time is therefore

Hence the total time for the entire flight is

3.18 + 1 = 4.18 hours