What is the farmula for years of ordinary annuity?

The formula for the present value of an ordinary annuity is ( PV = P \times \frac{1 - (1 + r)^{-n}}{r} ), where ( PV ) is the present value, ( P ) is the payment amount per period, ( r ) is the interest rate per period, and ( n ) is the total number of payments. For the future value of an ordinary annuity, the formula is ( FV = P \times \frac{(1 + r)^n - 1}{r} ). These formulas are used to calculate the value of a series of equal payments made at regular intervals.