Five bells begin to toll together and they toll at intervals of 6, 5, 7, 10 and 12 seconds

Five bells begin to toll together and they toll at intervals of 6, 5, 7, 10 and 12 seconds respectively. How many times they toll together in one hour excluding the one at the start?

  1. 7
  2. 8
  3. 9
  4. 10
Anurag Mishra Professor Asked on 19th April 2016 in Maths.
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  • 1 Answer(s)

    Answer: (2) 8 

    Solution:-
    L.C.M. of 6, 5, 7, 10 and 12 is 420.
    Then, the bells will toll together after every 420 seconds
    7 minutes.
    Now, 7 x 8 = 56 and 7 x 9 = 63.
    Thus, in 1-hour (or 60 minutes), the bells will toll together 8 times, excluding the one at the start.

    Hence, the correct answer is option (2) 8.

    Anurag Mishra Professor Answered on 24th April 2016.
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