How long does it take to double your money? (by Jeremy Zawodny)

The "Rule of 72" says that you take the interest rate (assuming that it's compounded annualy) and divide 72 by it. For an investment that yields 7% annual returns, that means 72 / 7 which is roughly 10.3 years.
How long does it take to double your money? (by Jeremy Zawodny): "How long does it take to double your money?"