Answer
$10^{-5}$
Work Step by Step
$a_1=100$ and we can see that the ratio of subsequent terms is $\frac{1}{10}$, thus $r=\frac{1}{10}$
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: $a_8=100\cdot(\frac{1}{10})^{8-1}=10^2\cdot10^{-7}=10^{-5}$
