Answer
$\frac{1}{4^9}$
Work Step by Step
We can see that the ratio of subsequent terms is $\frac{1}{4}$, thus $r=\frac{1}{4}$.
The nth term of a geometric series can be obtained by the following formula: $a_n=a_1\cdot r^{n-1}$, where $a_1$ is the first term and $r$ is the common ratio.
Hence here: $a_{12}=16\cdot(\frac{1}{4})^{12-1}=\frac{1}{4^9}$
