Question

    ST

    A motor-cycle covers 100 km with a speed of 50 km/hr.

    find the speed of the motor-cycle for the next 100 km journey so that the average speed of the whole journey will be 75 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 = 75 km/hr Using the formula, average speed = 2xy/(x + y) ⇒ x = speed of first 100 km = 50 km/hr ⇒ 75 = 2 × (50 × y)/(50 + y) ⇒ 150 km/hr

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