Ques. Four different electronic devices make a beep after every 30 minutes, 1 hour, 3/2 hour and 1 hour 45 minutes respectively. All the devices beeped together at 12 noon. They will again beep together at:
Op 1: 12 midnight
Op 2: 3 a.m.
Op 3: 6 a.m.
Op 4: 9 a.m.
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