A man rows a boat at 15 km/h in still water. If the river current flows at 3 km/h, how long will it take him to travel 60 meters downstream?

Explanation

The effective speed downstream is the sum of the boat's speed and the current speed: 15 + 3 = 18 km/h. Converting to meters per second: 18 × (1000/3600) = 5 m/s. Time to cover 60 meters = distance ÷ speed = 60 ÷ 5 = 12 seconds.