At the distance of 45 km from the shore, a hole is found in the ship which supply 4¼ tonnes of water in 15 min. Ship contains the extraction pump which remove the water from the ship at the rate of 12 tonnes/hr. 60 tonnes of water would sink it. The average speed of sailing to reach the shore just before sink is
Distance from the shore(d) = 45 km
Water enter per hour in ship by hole = 4¼ tonnes in 15 min = 4.25/0.25 = 17 tonnes
(? 1 hr = 60 min)
Water leaving the ship per hour by pump = 12 tonnes/hr
Amount of water remaining at the end of the hour = 17 - 12 = 5 tonnes/hr
Time taken to sink the ship = 60/5 = 12 hr
Average speed of sailing to reach the shore just before = Distance/Time = 45/12 = 3.75 km/hr
∴ The average speed of sailing to reach the shore just before sink = 3.75 km/hr