Question

The speed of an express train is x km per hr and speed of an ordinary train is 12 km per hr less than that of express train. If the ordinary train takes one hour longer than the express train to cover a distance of 240 km, find the speed of express train

Answer 1

Solution:

Let the time taken by express train to cover a distance of 240 km be 'y' hours and speed be 'x' km/h.

xy = 240

And ( x - 12 )( y + 1 ) = 240

=> xy - 12y - 12 + x = 240

=> x = 12y + 12

=> x = 12( y + 1 )

Since,

xy = 240

=> y( 12y + 12 ) = 240

=> y = 4

xy = 240

=> 4x = 240

=> x = 240/4 = 60 km/h

Thus, the speed of express train is 60 km/h.