Hi all,     I am working in a task to derive the interest rate using excel spreadsheet. Normally the interest rate (r) is derived using the SAS mort function - MORT( a, p, r, n), where a, p and n are already given. (a = amount, p = monthly payment, n = number of periods).  Reference: https://documentation.sas.com/doc/en/vdmmlcdc/8.1/ds2ref/n15243fav7jqr6n1amghnmw1vb8i.htm    Are there any methods to derive the interest rate (r) if it is unknown factor in excel? Or are there any alternative formula can be used?       Thanks.  ... View more