A plane flying against the wind covers the 900-kilometer distance between two aerodromes in 2 hours. The same plane flying with the wind covers the same distance in 1 hour and 48 minutes. If the speed of the wind is constant, what is the speed of the wind?

The speed of the wind is 25 km/hr.

Explanation:

Let us call the speed of the plane and the speed of the wind. When the plane is flying against the wind, it covers the distance of 900-km in 2 hours (120 minutes); therefore;

(1).

And when the plane is flying with the wind, it covers the same distance in 1 hour 48 minutes (108 minutes)

(2).

From equation (1) we solve for and get:

,

and by putting this into equation (2) we get:

or in km/hr this is

the results is a decrease in air temperature with an increase of altitude.

explanation: