Answer
$P = \frac{A~r}{(1+r)^t-1}$
The resulting formula describes the amount of the periodic deposit $P$ required in an annuity.
Work Step by Step
$A = \frac{P~[(1+r)^t-1]}{r}$
$P = \frac{A~r}{(1+r)^t-1}$
The resulting formula describes the amount of the periodic deposit $P$ required in an annuity if we want to end up with a final amount, $A$, with an interest rate of $r$ compounded annually for a time of $t$ years.
