Speed of a boat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to place at a distance of 210 km and comes back to the starting point. The total time taken by him is:	Pick.
A) 12 hours  B) 24 hours  C) 36 hours  D) 48 hours  E) none

Rationale: "sol . speed upstream = 7.5 kmph ; speed downstream = 10.5 kmph . ∴ total time taken = [ 210 / 7.5 + 210 / 10.5 ] hours = 48 hours . answer d"
Answer: D