19. If a man takes 4 hours to cover a distance of 15km, how much time will be needed to cover 63 km at the same speed:

20. A car travels a distance of 840 km at a uniform speed. If the speed of the car is 10km/hr more, if takes tow hours less to cover the same distance. The original speed of the care was:

21. A train is moving with a speed of 92.4 km/hr. How many metres will it cover in 10 minutes: