Question

A train covers a distance of 90 km at a uniform  speed. Had the speed been 15 km/hour more, it would have taken 30 minutes less for the journey. Find the original speed of the train.

Answer 1

Let the original speed of the train be x km/hr

Distance covered = 90 km.
⇒ Time taken by the train with original speed

Now, if the speed of the train is increased by 15 km/hr, the train takes 30 minutes less for the same journey

⇒ Speed of the train after increasing = (x+15) km/hr and the time taken by the train after