In engineering economy problems we want to know the rate of return on an investment that returns a series of equal annual palyments for n years. This is a simpler problem than the IRR function is designed for, since it deals with varying payments which must be spelled out in an array.

I don't want to put the same annual payment in 20 cells to use IRR, and I want the number of years to be a variable, which IRR would not lend itself to. Rate should be able to do this task in a single cell, but the results I am getting are not accurate.

Basically I want to find the interest rate that will make the present value of the annual payments equal to the initial investment.