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    Question

    The ratio of speed of boat in upstream and in Stillwater

    is 1: 3 respectively. The boat takes a total of 10 hours to travel 300 kilometer in downstream and 20 kilometre in upstream is. If speed of a boat in downstream is X kilometer per hour. Then the time taken by it to travel to 288 kilometer in stillwater will be.
    A (0.45x+5) hrs. Correct Answer Incorrect Answer
    B (x-8) hrs. Correct Answer Incorrect Answer
    C (0.6x+9)hrs. Correct Answer Incorrect Answer
    D (0.5x-8)hrs. Correct Answer Incorrect Answer
    E (2.5x-4)hrs. Correct Answer Incorrect Answer

    Solution

    Let the upstream speed and speed of boat in stillwater be a kilometer per hour and 3a kilometer per hour respectively. Therefore the speed of this stream = 2a Kilometer per hour. And downstream speed of the boat = 2a+3a= 5a Kilometer per hour. According to question, (300/5a) +(20/a) = 10 10a = 80 A=8 Therefore, downstream speed of the boat = 5a=40 a = 8 So X = 40. Time taken by boat To travel to 288 kilometre in Stillwater = 288/24 = 12 hours = ( 0.5*40 – 8 ) = ( 0.5x-8) hrs.

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