Spreadsheets such as Microsoft Excel and Google Sheets. Any time I want to do a "what-if" scenario that involves math, I create a new spreadsheet, and I set up

Spreadsheets such as Microsoft Excel and Google Sheets. Any time I want to do a "what-if" scenario that involves math, I create a new spreadsheet, and I set up a series of cells as the input parameters, and then I start creating formulas. You can try out anything math-based very quickly (algorithms, tax calculations, etc)