A man swims 12 km downstream and 10 km upstream. If he takes 2 hours each time, what is the speed of the stream?

0.5 Km/hr

Let the speed of the boat be x and the speed of the stream be y. 

[Downstream - D, Upstream - U]

Speed_D = \(\frac{12}{2 }\) = 6

Speed_U = \(\frac{10}{2 }\) = 5

We, know Downstream speed = x + y = 6 ...........(i)

Upstream speed = x - y = 5   ................(ii)

Subtracting both the equations: 

2y = 1

y = 0.5

The spread of the stream is 0.5 km/hr