In the investment world so many people wonder how long will it take to double their money at its current position. Well a lot of people never even heard of the rule I am about to explain. The rule is called the rule of 72 this is used to find how money you will in a certain time period. You use the rule of 72 by dividing 72 by the investment interest rate .Example of this would be if you had $10,000 in a mutual fund and the fund director said that fund a constant yield of 12% annual, now you would divide 72 by 12 and get 6 so if you bought that mutual fund it would take six years for your money to reach $20,000. I feel though this rule should be taught in elementary because it is a basic fundamental of investing ,so many adults have not heard of this rule.