If the future value after 5 years is 10 times more, or if it is the same as it was at the beginning of the five years period, or it is half of what it was the beginning of the five years period, use the relationship you have derived from the future value formula and validate the relationship in EXCEL in your second SHEET of your workbook. Specified with your own numbers and validate the equation after you find the return rate for the appropriate case using the RATE excel function. or in other words, (1+r)^ FVN PV. 1