A man travels 140 km by ship, 600 km by rail and 40 km by horse, taking an overall time of 15 hours 30 minutes. The speed of the train is 3 times that of the horse and 1^1/2 times that of the ship. Find the speed of the train.

If the speed of horse is x km/hr, then the speed of the train is 3x km/hr (speed of train is 3 times the speed of the horse)

Speed of the train = 1^1/2 of the speed of the ship = 3/2 of ship's speed, i.e. speed of ship = 3x/(3/2) = 2x km/hr

Total time taken is 15 hrs and 30 min = 15 + 30/60 = 15 + 1/2 = 31/2 hrs. Therefore, (140/2x) + (600/3x) + (40/x) = (31/2)

70/x + 200/x + 40/x = 31/2

310/x = 31/2

x = 20 Speed of the train is 3x = 3 * 20 = 60 km / hr.  It is the correct answer.