How Stocks Work Full Size Version Share | Have A Question About This Topic? Name Email Address Question Thank you! Oops! Related Contents 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. Estimating the Cost of College This worksheet can help you estimate the costs of a four-year college program. Impact of Taxes and Inflation Estimate the potential impact taxes and inflation can have on the purchasing power of an investment.