You have $100 to invest. If you can earn 12% interest, about how long does it take for your $100 investment to grow to $200? Suppose the interest rate is just half that, at 6%.

At half the interest rate, does it take exactly twice as long to double your money? Why or why not? How long does it take?
If the annual interest rate is 12 %, the number of years it takes to double your money is ______ years.