Algebra 1: Common Core (15th Edition)

Geometric, the ratio is $\frac{1}{3}$
You have the sequence:81,27,9,3. Find the common ratio by using the formula: R=$\frac{a2}{a1}$,R=$\frac{a4}{a3}$.Plug in the values to get the ratios r=$\frac{27}{81}$=$\frac{1}{3}$ r=$\frac{3}{9}$=$\frac{1}{3}$ There is a common ratio,r=$\frac{1}{3}$. So the sequence is geometric.