Question

The speed of boat in still water is 11 km/h. It can go 12 km upstream and return downstream to the original point in 2h 45mins. Find the speed of the stream.

Answer 1

Let the speed of stream be x

Speed of boat in still water = 11
Speed of boat upstream = 11-x
Speed of boat downstream = 11+x

Distance = 12
Distance/speed = time

12/(11-x) + 12/(11+x) = 2 hours 45min=2(3/4)hours
12*(22/(121-x*x) = 11/4
x*x = 25
x = 5

Speed of stream = 5km/hr