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If a radioactive isotope has half life of 5 days,how long will it take for its radioactive strength to be a maximum of one thousandth,(1/1000) of its original value?

Can anyone give me a VERY SIMPLE explanation of this please?

Thank you.

  • Science -

    Solve this equation for the number of days, x:

    (0.5)^(x/5) = 1/1000
    You can compute x by taking the log of both sides.
    x/5 = 9.97
    x = 49 days

    The words "a maximum of" are not needed in your question. After 49 days, the radioactive strength will be exactly 1/1000 of the original value, except for rounding-off error. You only have one significant figure in the half-life.

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