Question

a boat goes 16km upstream and 24 downstream in 6 hrs . it can go 12km up and 36km down in the same time.find the speed of the Boat in still water and the speed of the stream

Answer 1

let the time taken in going 12km upstream = time taken in going 36km downstream = t
=> speed of boat in upstream = 12/t
=>speed of boat in downstream = 36/t
=> time taken in going 16km upstream = 16/(12/t)
=>time taken in going 24km downstream = 24/(36/t)
=>total time taken in 16km upstream and 24km downstream
     =16/(12/t)+24/(36/t)=6 hours
by solving the equation
 t=3
so speed of boat upstream = 4km/h
and speed of boat downstream = 12km/h
let velocity of boat in still water = v
let speed of stream = b
-> v-b = 4
 v+b=12
=> v=8 and b=4
velocity of boat in still water = v =8km/h
and speed of stream =b= 4km/h