The plane moved at a speed of 720 kilometers per hour flew the distance between the two cities 2.25

The plane moved at a speed of 720 kilometers per hour flew the distance between the two cities 2.25 hundredths of an hour by how much it needed to increase the speed to reduce the flight time by 15 minutes.

Find the distance between the two cities.
We multiply the plane’s flight speed by the travel time.
720 * 2.25 = 1620 km.
We translate 15 minutes into hours.
15/60 = 1/4 = 0.25 hours.
We find the required flight time of the aircraft.
2.25 – 0.25 = 2 hours.
Determine the speed at which the plane should fly in order to reduce the time by 15 minutes.
Divide the distance between cities by 2 hours.
1620/2 = 810 km / h.
From this it follows that the aircraft must increase its speed by:
810 – 720 = 90 km / h.
Answer: 90 km / h.