A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream, it takes 4 hours. What is the speed of the boat in still water?
Answer: B
Rate downstream = 16/2 kmph = 8 kmph.
Rate upstream = 16/4 kmph = 4 kmph.
Speed in still water = 1/2 (8 + 4) kmph = 6 kmph.