The speed of a boat in downstream is 15 km/hr and the speed of current is 3 km/hr. Find the total time taken by the boat to cover 15 km upstream and 15 km downstream.

2 hrs 40 minutes

ATQ, Current speed = 3 km/hr

        Downstream speed [ Boat+current] = 15 km/hr

Boat speed + 3 km/hr = 15 km/hr

                  Boat speed = 12 km/hr

Now, downstream speed = 15 km/hr and upstream speed = 9 km/hr

Time to cover 15 km upstream = \(\frac{15}{9}\) = 1\(\frac{2}{3}\) hour or 1 hour 40 minutes

Time to cover 15 km downstream = \(\frac{15}{15}\) = 1 hour

                            Total time  = 2 hour 40 minutes