we know that a year has 12 months, so 1 year plus 8 more moths will be (12+8)/12 or 20/12 years, or 5/3 year.
[tex]~~~~~~ \textit{Simple Interest Earned Amount} \\\\ A=P(1+rt)\qquad \begin{cases} A=\textit{accumulated amount}\dotfill & \$70000\\\ P=\textit{original amount deposited}\dotfill & \$60000\\ r=rate\to r\%\to \frac{r}{100}\\ t=years\to \frac{20}{12}\dotfill &\frac{5}{3} \end{cases} \\\\\\ 70000=60000[1+(\frac{r}{100})(\frac{5}{3})]\implies \cfrac{70000}{60000}=1+(\frac{r}{100})(\frac{5}{3})[/tex]
[tex]\cfrac{7}{6}=1+\cfrac{5r}{300}\implies \cfrac{7}{6}=1+\cfrac{r}{60}\implies \cfrac{7}{6}-1=\cfrac{r}{60}\implies \cfrac{1}{6}=\cfrac{r}{60} \\\\\\ \cfrac{60}{6}=r\implies 10=r[/tex]
