Respuesta :
Using an exponential function, it is found that the substance is 7,535 years old.
What is the exponential function for the amount of a substance?
The function is given by:
[tex]A(t) = A(0)e^{-kt}[/tex]
In which:
- A(0) is the initial amount.
- k is the rate of exponential decay.
Carbon-14 has a half life of 5700 years, that is, A(5700) = 0.5A(0), hence we use this to find k.
[tex]A(t) = A(0)e^{-kt}[/tex]
[tex]0.5A(0) = A(0)e^{-5700k}[/tex]
[tex]e^{-5700k} = 0.5[/tex]
[tex]\ln{e^{-5700k}} = \ln{0.5}[/tex]
[tex]k = -\frac{\ln{0.5}}{5700}[/tex]
k = 0.00012160476
Hence:
[tex]A(t) = A(0)e^{-0.00012160476t}[/tex]
It was 40% of the amount when A(t) = 0.4A(0), hence we solve for t.
[tex]A(t) = A(0)e^{-0.00012160476t}[/tex]
[tex]0.4A(0) = A(0)e^{-0.00012160476t}[/tex]
[tex]\ln{e^{-0.00012160476t}} = \ln{0.4}[/tex]
[tex]t = -\frac{\ln{0.4}}{0.00012160476}[/tex]
t = 7535.
More can be learned about exponential functions at https://brainly.com/question/25537936
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