The rule of 72 states that if an investment earns $\displaystyle {P}$ % interest per year, it will take approximately $\displaystyle \frac{{72}}{{P}}$ years for your money to double.

You invest 6500 at 1.3 % interest annually. Round all answers to 2 decimal places.

According to the rule of 72, what is the doubling time, in years, for this investment Preview Question 6 Part 1 of 4  

Use the doubling time to find a formula for $\displaystyle {V}{\left({t}\right)}$, the value of your investment at time $\displaystyle {t}$. $\displaystyle {V}{\left({t}\right)}=$ Preview Question 6 Part 2 of 4  

According to the doubling time, how much will your investment be worth after 45 years? Preview Question 6 Part 3 of 4  

Use the compound interest formula to find how much the investment will be worth after 45 years. .

You may notice that your two values for the investment's worth after 45 years are different. That is because the doubling time you found with the rule of 72 is only an approximation. If the approximation were better, the two values would be the same.