As per the given data, we know In one direction Vinod will go by down-stream and return with up-stream and in both cases the distance is same ⇒ Downstream distance = Upstream distance ⇒ (U + 3) 4 = (U – 3)6 ⇒ 4U + 12 = 6U – 18 ⇒ 30 = 2U ⇒ U = 15 km/hr ∴ Speed of the Vinod in still water = 15 km/hr