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Question

Vivek sets alarm in two different clocks. The first alarm rings after 30 minutes and the second rings after every 90 minutes. If they rang together at 11pm, when is the earliest they will ring together again?

  • 12.30 am
  • 2 am
  • 1.30 am
  • 1.00 am
  • None of these
Answer- A

LCM of 30 and 90 = 90

Hence they will ring again earliest after 90 minutes.

Now 11pm + 90 min = 12.30 am


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