A man can row 6 km/h in still water. If the speed of the current is 2 km/h, it takes 3 hours more in upstream than in the downstream for the same distance. The distance is

Speed in still water $$=6km/h$$
Speed in upstream $$=6-2 = 4km/h $$
Speed in downstream $$ =6+2=8 km/h$$
Distance =d
Time taken while going downstream =t hours
Time taken while going upstream = t+3 hours
Since the distance is same
$$8\times t = 4 \times (t+3) = 4t +12$$
$$4t =12$$
$$t=3 hours$$
Distance = Speed in downstream $$\times$$ Time taken while going downstream
$$=8\times3$$
$$=24 km$$
Hence Option B is the correct answer.