The amount of annuity or future value S of an ordinary annuity of ₹R per period for n periods at the rate/per period is given by :

$P=S(i+1)^{-n}$ $S=R\begin{Bmatrix}\frac{(1+i)^n-1}{i}\end{Bmatrix}$ $S=R\begin{Bmatrix}\frac{1-(1+i)^{n-1}}{i}\end{Bmatrix}$ $R=\frac{Si}{(1+i)^n+1}$

$S=R\begin{Bmatrix}\frac{(1+i)^n-1}{i}\end{Bmatrix}$