Chapter 12, Problem 21T

(a)

To determine

To calculate: The function $x=f\left(t\right)$ if a certain radioactive material has a half-life of $100$ days and the amount of material present, $x$, satisfies $\frac{dx}{dt}=kx$.

(b)

To determine

To calculate: The time it takes for $90\%$ of the radioactivity to dissipate if a certain radioactive material has a half-life of $100$ days and the amount of material present, $x$, satisfies $\frac{dx}{dt}=kx$.