A friend tells you that her savings account doubled in 9 years. Use the Rule of 72 to estimate what the APR of her account was.
http://www.investopedia.com/terms/r/ruleof72.asp
The Rule of 72 is a quick method to estimate the time it takes for money to double in value, given a fixed interest rate.
To estimate the APR (Annual Percentage Rate) of her savings account using the Rule of 72, we divide 72 by the number of years it took for her savings to double.
In this case, her savings doubled in 9 years, so we divide 72 by 9:
72 / 9 = 8
Therefore, the estimated APR of her savings account is 8%.
To estimate the annual percentage rate (APR) using the Rule of 72, we can divide the number 72 by the number of years it took for your friend's savings account to double.
In this case, her savings account doubled in 9 years. So, by dividing 72 by 9, we can estimate the APR.
Let's calculate it:
72 ÷ 9 = 8
Therefore, an estimate of the annual percentage rate (APR) of your friend's savings account would be 8%.