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? Getting a Head Start on College Savings A few strategies that may help you prepare for the cost of higher education. 5 Smart Investing Principles Principles that can help create a portfolio designed to pursue investment goals.