The time taken by a boat to travel; `x' km upstream is twice the time taken by the same boat to travel `x' km downstream. If speed of the boat in still water is 12 km/h. what is the speed of current ? (in km/h)

Distance travelled by boat = $$x$$ km

Let speed of current = $$y$$ km/h

Speed of boat = 12 km/h

=> Downstream speed = $$(12 + y)$$ km/h and upstream speed = $$(12 - y)$$ km/h

Acc. to ques, time taken by a boat to travel; `x' km upstream is twice the time taken by the same boat to travel `x' km downstream

=> $$\frac{x}{12 - y} = 2 \times \frac{x}{12 + y}$$

=> $$\frac{1}{12 - y} = \frac{2}{12 + y}$$

=> $$12 + y = 24 - 2y$$

=> $$y + 2y = 3y = 24 - 12$$

=> $$y = \frac{12}{3} = 4$$ km/h