Question

How long does it take for an investment to double in value if it is invested at 8% per annum compounded monthly?

Answer 1

solve
\[2=(1+\frac{.08}{12})^{12t}\] for t

Answer 2

first step is
\[12t=\frac{\ln(2)}{\ln(1+\frac{.08}{12})}\]
second step is
\[ t=\frac{\ln(2)}{12\ln(1+\frac{.08}{12})}\]
third step is use a calculator