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    Question

    The alarms of two alarm clocks sound at regular

    intervals of 72 seconds and 80 seconds. If they beep together for the first time at 6:00 am, at what time will they beep again for the first time?
    A 6:19 AM Correct Answer Incorrect Answer
    B 6:17 AM Correct Answer Incorrect Answer
    C 6:15 AM Correct Answer Incorrect Answer
    D 6:12 AM Correct Answer Incorrect Answer

    Solution

    ATQ-   time of repeated beeps = 6:00+ LCM (72, 80) seconds = 6:00+720 seconds = 6:00 + 12 minutes = 6: 12 minutes AM

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