Question

    A train covers a certain distance at a speed of 72 km/h

    and the next same distance with a speed of 90 km/h and the next same distance with a speed of 120 km/h. find the average speed?
    A 60 km/hr Correct Answer Incorrect Answer
    B 63 km/hr Correct Answer Incorrect Answer
    C 90 km/hr Correct Answer Incorrect Answer
    D 75 km/hr Correct Answer Incorrect Answer

    Solution

    Since the distance is same in all the conditions. Therefore, Average speed = 3xyz/(xy + yz + zx) Average speed = 3 x 72 x 90 x 120/(72 x 90 + 90 x 120 + 120 x 72) Average speed = 3 x 72 x 90 x 120/(6480 + 8640 + 8640) = 2332800/25920 = 90 km/hr

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