Question

If the simple interest on ​$4000 for 8 years is ​$2240​, then what is the interest​ rate?

Answer 1

$~~~~~~ \textit{Simple Interest Earned} \\\\ I = Prt\qquad \begin{cases} I=\textit{interest earned}\dotfill & \ 2240\\ P=\textit{original amount deposited}\dotfill & \ 4000\\ r=rate\to r\%\to \frac{r}{100}\\ t=years\dotfill &8 \end{cases} \\\\\\ 2240 = (4000)(\frac{r}{100})(8) \implies 2240=\cfrac{32000r}{100}\implies 2240=320r \\\\\\ \cfrac{2240}{320}=r\implies 7=r$