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    Question

    Speed of a boat in still water is 4 times more than the

    speed of stream. If boat covers 108 km in downstream in 9 hours, then find the time taken by the boat to cover 80 km in upstream.
    A 12 hours Correct Answer Incorrect Answer
    B 10 hours Correct Answer Incorrect Answer
    C 8 hours Correct Answer Incorrect Answer
    D 9 hours Correct Answer Incorrect Answer
    E 7 hours Correct Answer Incorrect Answer

    Solution

    Let the speed of stream be ‘x’ km/hr. So, speed of boat in still water = 5 × x = 5x km/hr Downstream speed of boat = 5x + x = 6x km/hr According to question; 6x = 108/9 = 12 Or, x = 2 Upstream speed of the boat = 5x – x = 4x = 4 × 2 = 8 km/hr Required time taken = 80/8 = 10 hours

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