The Rule of 72 Do you know how long it may take for your investments to double in value? The Rule of 72 is a quick way to figure it out. Share | Related Content The Fed and How It Got That Way Here is a quick history of the Federal Reserve and an overview of what it does. Mutual Funds vs. ETFs Exchange-traded funds have some things in common with mutual funds, but there are differences, too. How Compound Interest Works Use this calculator to better see the potential impact of compound interest on an asset.