16. A speed of 55 m/sec, is the same as:

17. Two men start together to walk to a certain destination, one at 3.75 km an hour and another at 3 km an hour. The former arrives half an hour before the latter. The distance is:

18. A train covers a distance in 50 minutes, if it runs at a speed of 48 km per hour on a average. The speed at which the train must run to reduce the time of journey to 40 minutes, will be: