The nice thing about using a computer and spreadsheet is that you can experiment with numbers without having to RE-DO all the calculations. Lets change the interest rate and then the number of months. Once we have the formulas setup, we can change the variables that are called from the formula and watch the changes. Do that on paper and you better get your calculator back out and get an Eraser and hope you punched all the right keys and in the right order. Spreadsheets are instantly updated if one of the entries is changed.
Spreadsheets can be very valuable tools in business.