Four different devices beep after every half hour, 60 min, 1 and half hours, and 135 min respectively. All the devices beeped together at 12 noon. They will beep together again at:

 

  • Option 1)

     

    12 Midnight

     

  • Option 2)

     

    6 AM

     

  • Option 3)

     

    9 PM

     

  • Option 4)

     

    7: 30 AM

     

  • Option 5)

     

    9 AM

     

Answers (1)

A = 30 min

B = 60 min

C = 90 min

D = 105 min

LCM of ABCD = 1260 min or 21 hours

Required Time = 12 Noon + 21 => 9AM

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