The correct answer is that is will take 14 years for the savings account to double in value.
The rule of 70 is the concept that an investment will double in value in the amount of time that you get when you divide 70 by the annual interest rate. In this case you divide 70 by 5, which equals 14. Therefore, according to the rule of 70, it will take 14 years for this money to double in value.
