A swimmer can row 6 km/hr in still water and the speed of the stream is 2 km/hr. If the swimmer can cover a certain distance downstream and the same upstream in 75 minutes, then find the distance.

10 km

ATQ,  (D.S) Downstream speed = 6 + 2 = 8km/hr

         (U.S) Upstream speed = 6 - 2 = 4 km/hr

                               Distance =  \(\frac{D.S × U.S}{D.S + U.S}\) × Time

                                            =  \(\frac{8 × 4}{8 + 4}\) × \(\frac{75}{60}\)

                                            = \(\frac{32}{12}\) × \(\frac{15}{4}\) = 10 km