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    Question

    A plane can travel 36 km against the wind and 80 km with

    the wind in 4 hours. How much percent is the speed of the plane against the wind less than the speed with the wind, considering it can travel 168 km against the wind and 128 km with the wind in 11 hours?
    A 12% Correct Answer Incorrect Answer
    B 15% Correct Answer Incorrect Answer
    C 45% Correct Answer Incorrect Answer
    D 25% Correct Answer Incorrect Answer
    E none of these Correct Answer Incorrect Answer

    Solution

     ATQ, Let the againts the wind speed and with the wind speed of the plane be 'p' km/h and 'q' km/h, respectively. According to question: 36/p + 80/q = 4 ------------(i) And 168/p + 128/q = 11 -----------(ii) Solving (i) and (ii), we get p = 24 and q = 32 So, the upstream speed and the downstream speed of the boat are 24 km/h and 32 km/h respectively. So, the desired percentage = {(32 – 24)/32} × 100 = 800/32 = 25%

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