Question

    ST

    A motor-cycle covers 125 km with a speed of 60 km/hr.

    find the speed of the motor-cycle for the next 125 km journey so that the average speed of the whole journey will be 80 km/hr.
    A 117 km/hr Correct Answer Incorrect Answer
    B 150 km/hr Correct Answer Incorrect Answer
    C 120 km/hr Correct Answer Incorrect Answer
    D 88 km/hr Correct Answer Incorrect Answer
    E 90 km/hr Correct Answer Incorrect Answer

    Solution

    Average speed of whole journey = 80 km/hr Using the formula, average speed = 2xy/(x + y) ⇒ x = speed of first 125 km = 60 km/hr ⇒ 80 = 2 × (60 × y)/(60 + y) ⇒ 120 km/hr

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