New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    A train covers a certain distance at a speed of 40 km/h

    and the next same distance with a speed of 70 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 31.5 km/hr Correct Answer Incorrect Answer
    D 75 km/hr Correct Answer Incorrect Answer
    E 90 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 40 x 70 x 120/(40 x 70 + 70 x 120 + 40 x 120) Average speed = 3 x 40 x 70 x 120/(2800 + 8400 + 4800) = 1008000/16000 = 63 km/hr    

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