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    Question

    A boat running downstream covers a distance of 28 km in

    2 hrs while it covers the same distance upstream in 7 hrs. Then speed of the boat in still water is
    A 9 km/hr Correct Answer Incorrect Answer
    B 18 km/hr Correct Answer Incorrect Answer
    C 14 km/hr Correct Answer Incorrect Answer
    D 7 km/hr Correct Answer Incorrect Answer
    E 4 km/hr Correct Answer Incorrect Answer

    Solution

    Let the speed of boat in still water be a km/hr and that of stream be b km/hr. Therefore, 28/(a + b)= 2 ⇒ a + b = 14 ………..(i) 28/(a – b)= 7 ⇒ a + b = 4 ………..(ii) On adding, eq (i) and (ii) ⇒ 2a = 18 km/hr ⇒ a = 9 km/hr

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