If you deposit money today in an account that earns 10% annual interest, it will take you ________ years to double your money.

Do not round any intermediate work. Round your final answer to 2 decimal places (ex: if your answer is 12.345678 years, then you should enter 12.35). Margin of error for correct answers: +/- .03.

Do NOT use the "rule of 72" here -- a more precise answer is needed.