If you deposit money today into an account that pays 6.5 percent interest, how long will it take for you to double your money?

It depends on how often the interest is compounded. A little over 11 years if compounded once a year. 10 years and 9 months is compounded quarterly. An easy trick to remember is the rule of 72. Divide 72 by the interest rate and that is how long it will take to double your money. It doesn't work in all situations, but without doing TVM calculations, it is the most quick way.

Thank you for your help and the tip.