Answer:
If $T=1.65$ seconds, then we can solve the equation for $L$ as follows:
$$
T=1.1\sqrt{L}
$$
$$
\frac{T}{1.1}=\sqrt{L}
$$
$$
\left(\frac{T}{1.1}\right)^2=L
$$
Substituting $T=1.65$, we get:
$$
L=\left(\frac{1.65}{1.1}\right)^2=2.25
$$
Therefore, the length of the pendulum is approximately 2.25 feet.