Answer
Geometric with $r=\frac{1}{5}$
Work Step by Step
$125, 25, 5, 1,\frac{1}{5} ,\frac{1}{25} , . . .$
$\frac{a_2}{a_1}=\frac{25}{125}=\frac{1}{5}=r$
$ra_2=5=a_3$
$ra_3=1=a_4$
$ra_4=\frac{1}{5}=a_5$
and so on. The sequence is geometric with common ratio $r=\frac{1}{5}$.
