Answer :
Use the following formula for the final amount after t years:
[tex]A=P(1+\frac{r}{n})^{nt}[/tex]where,
P: principal investment
A = 2P (because you are interested in doubling the investment)
r: interest rate in decimal form = ?
t: time = 29
n: times at year for the compond interest = 1
Replace the previous values of the parameters into the formula for A and solve for r, as follow:
[tex]\begin{gathered} 2P=P(1+\frac{r}{1})^{1\cdot29} \\ 2=(1+r)^{29} \\ \sqrt[29]{2}=1+r \\ r=\sqrt[29]{2}-1 \\ r\approx0.024 \end{gathered}[/tex]Then, r is approximately 0.024, which corresponds to an interest rate of approximately 2.4%