Rule of 72?
An investment at a particular interest rate will double in a certain number of years. You can easily determine how quickly your investments will double simply by dividing 72 by the interest rate that you anticipate receiving in a given investment. For example, an investment that will yield 10% per year will double approximately every 7.2 years (72/10 = 7.2). A 12% yield would mean your investment doubles every 6 years (72/12 = 6). http://en.wikipedia.
