The formula for compounding continuously is :
[tex]A=Pe^{rt}[/tex]
where A is the future amount
P is the principal amount
e is a constant
r is the rate of interest
and
t is the time in years.
The question stated that the investment will be doubled, so the future amount will be twice the principal amount.
A = 2P
The rate of interest is 3.7%
e is a constant approximately equal to 2.71828..
Subsitute the values to the formula and solve the value of t :
[tex]\begin{gathered} A=Pe^{rt} \\ 2P=Pe^{0.037t} \\ 2=e^{0.037t} \end{gathered}[/tex]
Take the natural logarithm of both sides,
note that ln e = 1
[tex]\begin{gathered} \ln 2=\ln e^{0.037t} \\ \ln 2=0.037t\ln e \\ \ln 2=0.037t(1) \\ t=\frac{\ln 2}{0.037}=18.73 \end{gathered}[/tex]
The answer is 18.73 years
