A sailor sails a distance of 48 km along the flow of a river in 8 h. If it takes 12 h to return the same distance, then the speed of the flow of the river is?

Let speed of the flow of water be x km/h and rate of sailing of sailor be y km/h. Downstream speed (x + y) = 48/8 ⇒ x + y = 6 ....(i) and upstream speed x - y = 4 ...(ii) On solving Eqs. (i) and (ii), we get y = 1 km/h