The speed of a boat along the stream is 12 km/hr and against the stream is 8 km/hr. The time taken by the boat to sail 24 km in still water is?

A. 2 hrs

B. 3 hrs

C. 2.4 hrs

D. 1.2 hrs

Answer: Option C

Solution(By Examveda Team)

Speed of downstream
D = 12 km/h
Speed of upstream
U = 8 km/h
Speed of boat in still water
$$\eqalign{ & = \frac{{D + U}}{2} \cr & = \frac{{20}}{2} \cr & = 10\,km/h \cr} $$
Time taken by the boat in still water
$$\eqalign{ & = \frac{{24\,km}}{{10\,km/hr}} \cr & = 2.4\,{\text{hours}} \cr} $$