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 four-fifths of the same distance in still water?Solution
- Let the speed of boat in still water =B and speed of stream =S then Distance =D ATQ- 
D=9(B+S) … (1) 
D=18(B-S) … (2) Both directions distance is equal = 9(B+S) =18(B-S) 9B+9S=18B-18S 27S=9B S: B=1:3 =>B=3S So now- 
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