Annuities are series of equal periodic payments. Types: (1) Ordinary annuity (payments at period end); (2) Annuity due (payments at period beginning). Present value: PV = A × [(1-(1+r)^(-n))/r] (ordinary), or PV = A × [(1-(1+r)^(-n))/r] × (1+r) (due). Future value: FV = A × [((1+r)^n - 1)/r] (ordinary), or FV = A × [((1+r)^n - 1)/r] × (1+r) (due). Example: A=1000, r=10%, n=5 years (ordinary). PV = 1000 × 3.7908 = 3790.8. FV = 1000 × 6.1051 = 6105.1. Applications: Loan EMI, retirement planning, pension calculations. Exam tip: Identify annuity type from payment timing. Use present/future value formulas correctly. Practice: Derive formulas using geometric series.