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    Question

    The half-life of a radioactive substance is 10 days. The

    time in which only 1/8th of the original substance remains is:
    A 20 days Correct Answer Incorrect Answer
    B 30 days Correct Answer Incorrect Answer
    C 40 days Correct Answer Incorrect Answer
    D 80 days Correct Answer Incorrect Answer

    Solution

    When only 1/8 of the substance remains, it means 3 half-lives have passed because: (1/2)³ = 1/8 Each half-life is 10 days, so total time = 3 × 10 = 30 days. Therefore, the correct answer is 30 days.

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