$r_{0}=100{12\left({\sqrt[{t \over n}]{1 \over (1-i_{\%})^{t \over 12}}}\right)-12 \over n(1-y_{\%})},$

{\displaystyle r_{0}=100{12\left({\sqrt[{t \over n}]{1 \over (1-i_{\%})^{t \over 12}}}\right)-12 \over n(1-y_{\%})},}