Question

A motorboat whose speed in still water is 15 km h goes 30 km downstream and comes back in a total 4 hours 30 min. determine the speed of the stream 1) 3 kmph 2) 3.5 kmph 3) 4.5

Answer 1

Let the speed of the stream is u km/h

Then,

30/(15+u) + 30/(15-u) = 4.5

30*30/(225-u*u) = 4.5

225 - u*u = 200

u = 5 km/h