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Math Help - help needed half-life logrithms

  1. #1
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    help needed half-life logrithms

    the half life of sodium-24 is 14.9h. suppose a hospital buys a 40mg sample of sodium-24.
    a.) how much of the sample will remain after 48h?
    b.) how long will it be until only 1mg remains?
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  2. #2
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    First solve for A .

    Q = Q_0 \times A^t where t is in hours. So we have

    20 = 40 \times A^{14.9}
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  3. #3
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    how i do it if i were to put in logs into that equation and put it in my calculator?
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  4. #4
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    You do need to use logs here.

    20 = 40 \times A^{14.9}

    \frac{1}{2} = \times A^{14.9}

    From here apply

    a= b^c \implies c=\log_ba
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