The speed ofa boat in still water is 18 km/h and the speed of the current is 6 km/h. In how much time (in hours) will the boat travel a distance of 90 km upstream and the same distance downstream?
Speed of boat(v) =Â 18 km/h
Speed of the current(u) = 6 km/h
Speed in upstream = v - u = 18 - 6Â =12 km/h
Speed in downstream = v + u = 18 + 6 =24 km/h
Distance = 90 km
Time taken by boat = $$\frac{90}{12} +Â \frac{90}{24} = \frac{270}{24} = 11\frac{1}{4}$$
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