A boatman goes 60 km upstream and downstream in 9 hours. Time taken to cover a distance of 4 km downstream is equal to time taken to cover a distance of 2 km upstream. Find the speed of current (in km/hr).

5

\(\frac{4}{x + y}\) = \(\frac{2}{x - y}\)

4x - 4y = 2x + 2y

2x = 6y 

x : y = 3 : 1

\(\frac{60}{x + y}\) + \(\frac{60}{x - y}\) = 9

\(\frac{60}{4R}\) + \(\frac{60}{2R}\) = 9

R = 5

Speed of current = 5 km/hr