3. How long will it take to double your money if it grows at 12 percent annually?

The "Rule of 72" gives a quick answer to the question. According to the rule, divide 72 by the interest rate percentage and this is the approximate number of years it takes the money to double (i.e., 72/12 = 6.0 years). Also, divide 72 by the number of periods to find the approximate interest rate per period required to double your money.

4. David Riley bought a stock 10 years ago for $10.00 a share. If it is now selling for $50.00 a share, what is the stock price's compound annual growth rate?

5. You may purchase a three-year certificate at the local savings and loan association for $500. The note pays no interest but will be redeemed for $1000 at maturity. What is the interest rate on the note?

6. Ann Barry sold a farm for $10,000 per acre. She says she owned the land for 20 years and that the value of the property appreciated at an 11 percent annual rate. What did Ann originally pay for the land?