Question

Money borrowed at 15% simple interest. After one year, $678.50 pays off the loan. How much was originally borrowed?

Answer 1

`\bf ~~~~~~ \textit{Simple Interest Earned Amount} \\\\ A=P(1+rt)\qquad \begin{cases} A=\textit{accumulated amount}\to &\$678.50\\ P=\textit{original amount deposited}\\ r=rate\to 15\%\to (15)/(100)\to &0.15\\ t=years\to &1 \end{cases} \\\\\\ 678.50=P(1+0.15\cdot 1)\implies 678.50=P(1.15)\implies \cfrac{678.50}{1.15}=P`