Question

Sophia deposited $80,000 in a savings account with simple interest. One year later, she had earned $12,000 in interest. What was the interest rate?

Answer 1

`~~~~~~ \textit{Simple Interest Earned} \\\\ I = Prt\qquad \begin{cases} I=\textit{interest earned}\dotfill & \$ 12000\\ P=\textit{original amount deposited}\dotfill & \$80000\\ r=rate\to r\%\to (r)/(100)\\ t=years\dotfill &1 \end{cases} \\\\\\ 12000 = (80000)((r)/(100))(1) \implies \cfrac{12000}{80000}=\cfrac{r}{100} \\\\\\ \cfrac{3}{20}=\cfrac{r}{100}\implies \cfrac{300}{20}=r\implies \stackrel{ \% }{15}=r`