Solution:

Let the speed of stream be x km/hr

Given, speed of boat in still water is .

So, speed of downstream

And, speed of upstream

Using, speed = distance/ time

Time taken by the boat to go km upstream

And, time taken by the boat to return km downstream

From the question, the boat returns to the same point in hr.

[by factorisation method]

∴

x

As the speed of the stream can never be negative, only the positive solution is considered.

Therefore, the speed of the stream is km/hr.