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    Question

    A boat travels the same distance 'd' km in both upstream

    and downstream directions, taking a total of 15 hours for the round trip. If the downstream speed of the boat is 16 km/hr and the upstream speed is 8 km/hr, calculate the time required for the boat to cover '1.5d' km in still water.
    A 12 hrs Correct Answer Incorrect Answer
    B 10 hrs Correct Answer Incorrect Answer
    C 11 hrs Correct Answer Incorrect Answer
    D 8 hrs Correct Answer Incorrect Answer
    E 15 hrs Correct Answer Incorrect Answer

    Solution

    ATQ,  d/16 + d/8 = 15 Or, {d + 2d)/16} = 15 Or, 3d = 15 X 16 Or, 3d = 240 So, 'd' = (240/3) = 80 Speed of boat in still water = average of speed of boat in downstream and in upstream = (16 + 8)/2 = 12 km/hr   So, required time = 80 x 1.5/12 = 10 hrs 

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