A man rows a boat such that the time taken to travel a certain distance upstream is double the time taken to cover the same distance downstream. If the boat's speed in still water is 42 km/h, what is the velocity of the current?

Explanation

Given that the upstream time is twice the downstream time, the ratio of upstream to downstream speeds is 1:2. Using the formula for speeds, (boat speed + stream speed) / (boat speed - stream speed) = downstream speed / upstream speed = 2. Solving for the stream speed with the boat speed at 42 km/h yields 14 km/h.