4. A man crosses a street 600 m long in 5 minutes. His speed in km. per hour is:

5. Excluding stoppages, the speed of a bus is 54 km/hr and including stoppages, it is 45 km/hr. Fir how many minutes does the bus stop per hour:

6. A car covers four successive three km stretches at speeds of 10km/hr, 20 km/hr, 30 km/hr respectively. Its average speed over this distance is: