the speed of a boat in still water is 11km/hr./it can go 12km upstream and return downstream to the original point in 2hours45minutes.find the speed of the stream.
let the speed is x. so we have total distance = total time * speed
total distance is 24 km
during upstream speed is 11 + x so time = 12 / 11+x
during downstrem speed is 11 - x so time is = 12 / 11 - x
we have 12 / 11+x + 12 / 11 - x = 2hours45minutes = 11 / 4
solving we get x = 5 km/hr