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 Should You Invest in Exchange Traded Funds? There are hundreds of ETFs available. Should you invest in them? What’s Your Investment IQ? You make decisions for your portfolio, but how much do you really know about the products you buy? Try this quiz 5 Smart Investing Strategies Getting what you want out of your money may require the right game plan.