Example:Using a financial calculator, here's an example of how you'd find the PV of a $1,000 cash flow (FV) to be received in 5 (N) years, given a discount rate of 9% (I/Y).
N = 5, I/Y = 9, FV = 1,000; CPTPV = $649.93 (ignore the sign).
 
b: Calculate an unknown variable, given the other relevant variables, in single-sum problems.
Example 1:Solving for I/Y
In this example, you want to find the rate of return (I/Y) that you'll have to earn on a $500 investment (PV) in order for it to grow to $2,000 (FV) in 15 years (N). This very same problem could also be set up in terms of growth rates - e.g., what rate of growth (I/Y) is necessary for a company's sales to grow from $500 per year (PV) to $2,000 per year (FV) in 15 years (N).?
?
N = 15, PV = -500, FV = 2,000; CPTI/Y = 9.68%
?
Example 2:Solving for N