A. Since EE bonds are sold at half their face value, a $1,000 face value EE Savings bond will initially cost $500.

B. The “Rule of 72” states that an investment will double every time the number of years multiplied by the interest rate (in percent) equals seventy-two. For example, an 8% return that you hold for 9 years should double (8 * 9 = 72). Using the rule of 72, it will take approximately 20 years to double in value or 72/3.6 = 20.

Using your calculator, set your Present Value PV to -$500, your Future Value FV to $1,000, your interest rate I = 3.6%, and solve for N. Your answer is 19.6 years.