Question

Marie earns $96 in interest each year on an investment what is the rate of simple interest if her principal was $800

Answer 1

$\bf ~~~~~~ \textit{Simple Interest Earned}\\\\ I = Prt\qquad \begin{cases} I=\textit{interest earned}\to &\ 96\\ P=\textit{original amount deposited}\to& \ 800\\ r=rate\to r\%\to \frac{r}{100}\\ t=years\to &\stackrel{each~year}{1} \end{cases} \\\\\\ 96=800(r)(1)\implies \cfrac{96}{800}=r \\\\\\ 0.12=r\implies r\%=100\cdot 0.12\implies r=\stackrel{\%}{12}$