$P_{x}=P_{0}\left(1+{pr_{\%}(1-y_{\%}) \over 12}\right)^{t \over p}(1-i_{\%})^{t \over 12},$

{\displaystyle P_{x}=P_{0}\left(1+{pr_{\%}(1-y_{\%}) \over 12}\right)^{t \over p}(1-i_{\%})^{t \over 12},}