Solve.

How long will it take for the population of a certain country to triple if its annual growth rate is $4.7 \%$ ? Round to the nearest year.
$20 \mathrm{yr}$
$64 \mathrm{yr}$
$11 \mathrm{yr}$
$23 \mathrm{yr}$

Step 1 ：Given that the population of a certain country triples, we can denote the initial population as \(P = 1\) for simplicity.

Step 2 ：The final population after tripling is \(A = 3 \times P = 3\).

Step 3 ：The annual growth rate is given as \(4.7\% = 0.047\) in decimal form.

Step 4 ：The growth rate is compounded annually, so \(n = 1\).

Step 5 ：We can use the formula for compound interest to solve for the time \(t\), which is \(t = \frac{\ln(A/P)}{n \times \ln(1 + r/n)}\).

Step 6 ：Substituting the given values into the formula, we get \(t = \frac{\ln(3/1)}{1 \times \ln(1 + 0.047/1)}\).

Step 7 ：Calculating the above expression, we get \(t \approx 24\).

Step 8 ：Rounding to the nearest year, we get \(t = 24\).

Step 9 ：Final Answer: The time it will take for the population of the country to triple, given an annual growth rate of \(4.7\% \), is approximately \(\boxed{24}\) years.