when a plane flies against the wind, it can travel 1000 km in 5 hours. When it flies with the wind, it can travel the same distance in 4 hours. Find the rate of the plane in still air and the rate of the wind.

Solution:

    Let the rate of plane = x kmph

                 rate of wind = y kmph

                 x - y = 1000/5 = 200

                 x + y = 1000/4 = 250

       Adding the above two equations:    2x = 450

                                                                     x = rate of plane = 225 kmph

                                                                     y = rate of wind = 25 kmph