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    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 three-fifths of the same distance in still water?
    A 7.2h Correct Answer Incorrect Answer
    B 6.6h Correct Answer Incorrect Answer
    C 3.8h Correct Answer Incorrect Answer
    D 7.9h Correct Answer Incorrect Answer

    Solution

    Let the speed of boat in still water =B and speed of stream =S then Distance =D ATQ- 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- Take time Three-fifths of the same distance in still water=(D/B)×3/5 =9(B+S) ×3/5 /B =[9(3S+S) ×3/5]/3S =36/5=7.2hours.

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