A boat takes 5 hrs to cover a distance of 30 km in downstream while it takes 01 hr extra to cover the same distance in upstream. Find speed of boat in still water.

5.5 km/hr

Let speed of boat = x

Let speed of stream = y

Speed = \(\frac{Distance}{Time}\)

Speed of boat in downstream (x + y) = \(\frac{30}{5}\) = 6 ....(i)

Speed of boat in Upstream (x - y) = \(\frac{30}{5 + 1}\) = 5 .....(ii)

Add (i) and (ii)

x + y = 6

x - y = 5

2x    = 11

x     = 5.5 

Speed of boat in still water = 5.5 km/hr