Give stream of consciousness and then the final answer. Calculate the speed of a boat in still water (in km/hr) if in one hour, the boat goes 13 km/hr downstream and 10 km/hr upstream.
Options:
(A) 3 kmph
(B) 9 kmph
(C) 4 kmph
(D) 8 kmph
(E) 6 kmph
Speed in still water = (13 + 5)1/2 kmph = 9 kmph.
The final answer: (B).