Answer
Geometric,
$a_{1}=\dfrac{1}{2}
\text{ and }\\
r=\dfrac{1}{5}
$
Work Step by Step
The sequence $\left\{
\dfrac{1}{2},\dfrac{1}{10},\dfrac{1}{50}
\right\}$ is a geometric sequence with
\begin{array}{l}
a_{1}=\dfrac{1}{2}
\text{ and }\\
r=\dfrac{1}{5}
.\end{array}