Use Rule 72 to estimate the doubling time in years for the interest rate and then calculate exactly: 6% compounded annually need to calculate the answer for Rule 72 in years and then the Exact number in years.

and

Find the effective rate of the compound interest rate or investment: 24% compounded monthly (Note rate is a typical credit card interst rate often stated as 2.0% per month) Calculate the effective rate.

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