Question

Respective ratio of speed of boat in upstream and downstream is 4:9 then what is respective ratio of speed of boat and speed of current?

Answer 1

Let the speed of boat = v
And, speed of the river = u
Now, speed of the boat in upstream = v-u
And in downstream = v+u
Given,ratio = 4÷9
v-u÷v+u = 4 ÷ 9
9×(v-u) = 4×(v+u)
9v-9u = 4v+4u
5v= 13u
v/u = 13/5 final answer.

Answer 2

Let the speed of boat be x and the speed of river current be y

Now,

Relative speed of boat when it travels upstream is = x-y

Relative speed of boat when it travels downstream is = x+y

As per the condition

(x-y)/(x+y) = 4/9

9x -9y = 4x +4y

5x = 13y

x/y = 13/5

Ratio of speed of boat and water current = 13/5

Hope this helps !!!!!!!!!!!!!!!!!!