Downstream speed of the boat = 12 km/hr Upstream speed of the boat = 6 km/hr Formula Used: Speed of boat in still water = Speed of (Upstream + Downstream)/2 Calculation: According to the question Speed of the boat in still water =
(12+6)
2
⇒ 9 km/hr Now, we have to find the time taken by the boat to cross 27 km in still water, ⇒Time =