Question

After one quarter (year), the interest on a principal of $1000 is $8.75.

Find the rate. Write your answer as a percent.

Answer 1

`~~~~~~ \textit{Simple Interest Earned} \\\\ I = Prt\qquad \begin{cases} I=\textit{interest earned}\dotfill & \$8.75\\ P=\textit{original amount deposited}\dotfill & \$1000\\ r=rate\to r\%\to (r)/(100)\\ t=years\dotfill &(1)/(4) \end{cases} \\\\\\ 8.75 = (1000)((r)/(100))((1)/(4))\implies 8.75=\cfrac{10r}{4} \\\\\\ 8.75=\cfrac{5r}{2}\implies 17.5=5r\implies \cfrac{17.5}{5}=r\implies \stackrel{\%}{3.5}=r`