A method for judging solar without the federal tax credit: payback time and 25-year net savings at three electricity rates, plus what these estimates leave out.
Break down the cost of a 3D print into filament, electricity, printer wear, labor and failures, with two worked examples and a pricing formula.
A cubic yard of concrete is about 90 bags of 40 lb, 60 bags of 60 lb or 45 bags of 80 lb. See where the numbers come from and how to choose a bag size.
Markup and margin both describe profit, but they divide by different numbers. Here are the formulas, worked examples and a conversion table.
How eBay seller fees work in 2026: the final value fee, the per-order fee and worked examples. Learn what you keep from a sale.
