the second document is the reading attached to the question.

Suppose you put money in a 3-year bank CD (certificate of deposit) which pays 2% per year. If you plan on repeatedly opening new 3-year CD's (every time one runs out), and want to keep doing that until your original money doubles, then how may times do you have to open a 3-year CD? You may want to show/explain your work for the possibility of partial credit. Edit View Insert Format Tools Table 12pt Paragraph BIUA 2v Tv|| p O words > % 0 *** 3. The "Rule of 72" It's not really a "rule, so this is a nickname, but this rule of thumb works very well. If a number of years multiplied by an investment growth rate equals 72, (for example 9 years times 8%), then if you had an investment which actually experienced that time and growth rate, the investment value would have doubled. So how long would an account growing at 6% per year need in order to double in value? 72/6 = 12 years. It's a handy rule if you're nowhere near electronics and find yourself wanting to perform "double your money" calculations. (And it's a mandatory topic for the CFP certification.)