What is the key economic principle involved in calculating the present value and future value of multiple

Question:

What is the key economic principle involved in calculating the present value and of multiple cash flows?

Future Value
Future value (FV) is the value of a current asset at a future date based on an assumed rate of growth. The future value (FV) is important to investors and financial planners as they use it to estimate how much an investment made today will be worth...