Question

Anna and Matt each opened a savings account with a deposit of $100.
Anna earned 4.5% simple interest per year.
Matt earned 3% simple interest per year.
Neither of them made additional deposits or withdrawals.
How much more did Anna receive in interest than Matt after 3 years?

Answer 1

$~~~~~~ \stackrel{\textit{\Large Anna}}{\textit{Simple Interest Earned Amount}} \\\\ A=P(1+rt)\qquad \begin{cases} A=\textit{accumulated amount}\\ P=\textit{original amount deposited}\dotfill & \ 100\\ r=rate\to 4.5\%\to \frac{4.5}{100}\dotfill &0.045\\ t=years\dotfill &3 \end{cases} \\\\\\ A=100[1+(0.045)(3)]\implies A=100(1.135)\implies A=113.5 \\\\[-0.35em] ~\dotfill$

$~~~~~~ \stackrel{\textit{\Large Matt}}{\textit{Simple Interest Earned Amount}} \\\\ A=P(1+rt)\qquad \begin{cases} A=\textit{accumulated amount}\\ P=\textit{original amount deposited}\dotfill & \ 100\\ r=rate\to 3\%\to \frac{3}{100}\dotfill &0.03\\ t=years\dotfill &3 \end{cases} \\\\\\ A=100[1+(0.03)(3)]\implies A=100(1.09)\implies A=109 \\\\[-0.35em] ~\dotfill\\\\ \stackrel{Anna}{113.5} - \stackrel{Matt}{109}\implies 4.5$