Question

Audrey deposited $40,000 in a savings account with simple interest. Five years later, she had earned $30,000 in interest. What was the interest rate? FIRST ONE TO ANSWER GETS BRANIEST

Answer 1

$~~~~~~ \textit{Simple Interest Earned} \\\\ I = Prt\qquad \begin{cases} I=\textit{interest earned}\dotfill&\ 30000\\ P=\textit{original amount deposited}\dotfill & \ 40000\\ r=rate\to r\%\to \frac{r}{100}\\ t=years\dotfill &5 \end{cases} \\\\\\ 30000=(40000)(\stackrel{\%}{\frac{r}{100}})(5)\implies \cfrac{30000}{(40000)(5)}=\cfrac{r}{100}\implies \cfrac{3}{20}=\cfrac{r}{100} \\\\\\ \cfrac{300}{20}=r\implies \stackrel{\%}{15}=r$