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    Question

    A boat covers a total downstream distance of 180 km,

    split into two equal parts. The boat’s speeds in these two parts are 2a km/h and 4a km/h respectively. The speed of the stream is a km/h. If the total time taken by the boat is 15 hours, find the value of ‘a’.
    A 1.5 Correct Answer Incorrect Answer
    B 3.2 Correct Answer Incorrect Answer
    C 4.5 Correct Answer Incorrect Answer
    D 8.5 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Speed of the boat downstream = (2a + a) = 3a km/h and (4a + a) = 5a km/h respectively.

    According to the question,

    90/3a + 90/5a = 15

    30/a + 18/a = 15

    48/a = 15

    a = 3.2

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