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1. Three sirens wail at intervals of thirty minutes, fifty minutes and thirty five minutes. If they wail together at 7.18 a.m. on Monday, what time and day will they wail together again?
2. Four bells ring at interval 24 seconds, 27 seconds, 30 seconds and 36 seconds. If four bells rang simultaneously at 7:00 am at what time will they ring together again?