A man rows a boat upstream and covers a distance of 8 km in 2 hour. When he rows the boat downstream, he covers the same distance in 80 minutes. The speed of the boat in still water is :

5 km/hr

The correct answer is Option (2) → 5 km/hr

Speed of boat in still water = x km/hr

Speed of current = y km/hr

Speed of upstream = $\frac{Distance}{Time}=\frac{8}{2}=4km/hr$

$⇒x-y=4$   ...(1)

$x+y=6$   ....(2)

Add (1) and (2)

$2x=10$

$x=5km/hr$