[tex] \bf ~~~~~~ \textit{Simple Interest Earned}
\\\\
I = Prt\qquad
\begin{cases}
I=\textit{interest earned}\dotfill&\$3150\\
P=\textit{original amount deposited}\dotfill & \$5000\\
r=rate\to r\%\to \frac{r}{100}\\
t=years\dotfill &9
\end{cases}
\\\\\\
3150=5000r(9)\implies 3150=45000r\implies \cfrac{3150}{45000}=r\implies 0.07=r
\\\\\\
r\%=0.07\cdot 100\implies r=\stackrel{\%}{7} [/tex]
The simple interest formula is I=PRT. Plug all of the numbers in.
Interest = 3150
Principal = 5000
Rate = r
Time = 9
3150 = (5000)(r)(9)
Simplify.
3150 = 45000(r)
Divide both sides by 45000.
.07 = r
Move the decimal two places to the right to make it a percentage.
7%
