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    Question

    A motor-cycle covers 160 km with a speed of 70 km/hr.

    find the speed of the motor-cycle for the next 170 km journey so that the average speed of the whole journey will be 90 km/hr.
    A 150 km/hr Correct Answer Incorrect Answer
    B 126 km/hr Correct Answer Incorrect Answer
    C 120 km/hr Correct Answer Incorrect Answer
    D 140 km/hr Correct Answer Incorrect Answer

    Solution

    Average speed of whole journey = 90 km/hr Using the formula, average speed = 2xy/(x + y)  x = speed of first 160 km = 70 km/hr 90 = 2 x (70 x  y)/(70 + y) = 126 km/hr

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