Mahesh can row a certain distance upstream in 9 hours and downstream the same distance in 6 hours. If the speed of stream is 3 km/hr, then find the speed of Mahesh rowing in still water?

15 km/h

                 Upstream(U.S)   :      Downstream (D.S)

Time:                9                 :              6

Time:                3                 :              2

Speed:             2                 :              3                  (Inverse relation)

Speed of Boat : Speed of Stream= \(\frac{3\;+\;2}{2}\) : \(\frac{3\;-\;2}{2}\) = 5 : 1

Here,

1R = 3 km/hr (given)

Therefore, speed of Boat = 5 x 3 = 15 km/hr