Barnett/Ziegler/Byleen Finite Mathematics 12e
Step 2. If a single payment is involved, determine whether simple or compound interest is used. Simple interest is usually used for durations of a year or less and compound interest for longer periods.
Step 3. If a sequence of periodic payments is involved, determine whether the payments are being made into an account that is increasing in value -a future value problem - or the payments are being made out of an account that is decreasing in value - a present value problem. Remember that amortization problems always involve the present value of an ordinary annuity.