Question

the speed of a boat in water is 15 km per hour it can go 45 km upstream and return downstream to the starting point in 6 hours 45 minutes find the speed of the stream

Answer 1

Let the speed of stream be x km/hr

Speed of boat in still water= 15 km/hr

speed of boat upstream= 15-x

Speed of boat downstream= 15+x

45/(15-x) + 45/(15+x) = 6 ¾

45(1/(15-x) + 1/(15+x)) = 27/4

30/225-x^2=27/4*45

5400=6075-27x^2

675=27x^2

X^2=25

X=5

speed of the stream= 5km/hr