Pre Calculus

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Exponential Growth and Decay

Find the half-life of a radioactive substance that decays by 5% in 9 years.

  • Pre Calculus -

    x = xi e^-kt
    .95 = e^-9 k
    ln .95 = -9k
    k = .005699

    .5 = e^-.005699 t
    ln .5 = - .005699 t
    t = 121.6 years

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