A boat travels 6 km in one hour when there is no current. However, it takes three times longer to cover the same distance going against the current. What is the speed of the current?

Explanation

The boat's speed in still water is 6 km/hr. Since it takes three times longer to travel the same distance against the current, the speed against the current is 6 ÷ 3 = 2 km/hr. Let the current's speed be x km/hr. Therefore, 6 - x = 2, which gives x = 4 km/hr.