The speed of a swimmer is 4 km h - 1 in still water. If the swimmer makes his strokes normal to the flow of river of width 1 km , he reaches a point 750 m down the stream on the opposite bank. The speed of the river water is ______ km h - 1 .

Step-by-step solution

Let v r be velocity of river and v m be velocity of man. Time taken by man to cross the river of width = 1000   m is t = 1 4   h . Now, drift x = v r × t ⇒ 0 . 750 = v r × 1 4 ⇒ v r = 3   km   h - 1