Using the rule of 72, t=72/r, how long will it take for the principal to double with an annual compound interest rate of 6%?

12 years

Step-by-step explanation:

r = compound interest rate in percent

t = doubling time in years

t = (72percent years) / (6 percent) = 12 years

As a curious cultural fact, there is a connection between the 72 and the fact that ln (2) = 0.69314718055. The constant is 69.3 for continuous compounding ...