2. Sample Papers
  3. Railways
  4. Quantitative Aptitude
  5. LCM & HCF

Railways Quantitative Aptitude LCM & HCF Sample Paper HCF and LCM Sample Test Paper-2

  • question_answer
    Three bells begin tolling at the same time and continue to do so at intervals of 21, 28 and 30 seconds respectively. The bells will toll together again after

    A)  7 seconds                     

    B)  420 seconds

    C)  630 seconds     

    D)  1764 seconds

    Correct Answer: B

    Solution :

    [b] The time after which they will toll together again must be a multiple of 21, 28 and 30. Hence, the L.C.M. of 21, 28 and 30 = 420 seconds which is the required time.


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