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    Question

    A boat running downstream covers a distance of 30 km in

    3 hrs while it covers the same distance upstream in 5 hrs. Then speed of the boat in still water is
    A 6 km/hr Correct Answer Incorrect Answer
    B 8 km/hr Correct Answer Incorrect Answer
    C 12 km/hr Correct Answer Incorrect Answer
    D 4 km/hr Correct Answer Incorrect Answer
    E 9 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, 30/(a + b)= 3 ⇒ a + b = 10 ………..(i) 30/(a – b)= 5 ⇒ a + b = 6 ………..(ii) On adding, eq (i) and (ii) ⇒ 2a = 16 km/hr ⇒ a = 8 km/hr

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