If a women goes 18 km downstream in 4 hrs and returns against the stream in 12 hrs, then the speed of the stream in Km/hr is

1.5

Speed of boat in still water - x

Speed of stream/current - y

Downstream speed i.e. x + y =  \(\frac{18 }{ 4}\) = 4.5 km/hr ----(1)

Upstream speed i.e. x - y = \(\frac{18 }{ 12}\) = 1.5 km/hr -----(2)

Subtracting 2 from 1

x + y - ( x - y ) = 4.5 - 1.5

x + y - x + y = 3

2y = 3

y = 1.5 km/hr