Question

A population of 40,000 decreases by 3.1% each year. what is the approximate population in 4 years

Answer 1

$\bf \textit{Amount of Population Decay} \\\\ A=Pe^{-rt}\qquad \begin{cases} A=\textit{accumulated amount}\\ P=\textit{initial amount}\dotfill &40000\\ r=rate\to 3.1\%\to \frac{3.1}{100}\dotfill &0.031\\ t=\textit{elapsed time}\dotfill &4\\ \end{cases} \\\\\\ A=4000e^{-0.031(4)}\implies A=40000e^{-0.124}\implies A=\cfrac{4000}{e^{0.124}} \\\\\\ A\approx 35335.194\implies \stackrel{\textit{rounded up}}{A\approx 35335}$