A boatman rows 1 km in 5 minutes along the stream and 6 km in 1 hr against the stream. The speed of the stream is

3 Km/hr

Speed of boat in still water - x

Speed of stream/current - y

Downstream speed i.e. - x + y -  \(\frac{1 }{5/60 }\) = 12 km/hr -----(1)

Upstream speed i.e. - x - y -  \(\frac{6 }{1 }\) = 6 km/hr ---------(2)

Subtracting 2 from 1,

x + y - x + y = 6

2y = 6

y = 3km/hr