C Future sum. The present value formula for annual or any period really interest. You figure simple interest on the principal which is the amount of money borrowed or on deposit using a basic formula.
N Number of periods.
Alternatively the function can also be used to calculate the present value of a single future value. Occasionally you will see that the term interest rate is sometimes referred to as a discount rate when discussing present value. In formula terms this would be 1 1i n. We see that the present value of receiving 1000 in 20 years is the equivalent of receiving approximately 14900 today if the time value of money is 10 per year compounded annually.