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    Question

    Four lights blink at intervals of 18 seconds, 24

    seconds, 36 seconds, and 48 seconds respectively. How many times will all the lights blink together in 3 hours?
    A 90 Correct Answer Incorrect Answer
    B 75 Correct Answer Incorrect Answer
    C 65 Correct Answer Incorrect Answer
    D 45 Correct Answer Incorrect Answer

    Solution

    ATQ,

    All the lights will blink together after 144 seconds (LCM of 18, 24, 36 and 48)

    3 hours = 180 minutes

    Therefore, required number of times ≤ (180 × 60) ÷ 144 = 75

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