A man rows a boat a certain distance downstream in 9 hours, while it…

Question

A man rows a boat a certain distance downstream in 9 hours, while it takes 18 hours to row the same distance upstream. How many hours will it take him to row 3/5 of the same distance in still water?

Accepted Answer

Option B. 7.2. Answer & Solution Answer: Option B Solution: & Speed of boat = x & Speed of stream = y & Distance = 9 ( x + y ) = 18 ( x - y ) & x + y = 2x - 2y & x = 3y & Distance = 9 ( x + y ) & = 9 ( 3y + y ) & = 36y & 36y × 3/5 = t × x & 36y × 3/5 = t × 3y & t = 365 = 7.2