Which explains why the sequence 81, 3, 1/9, . . . is arithmetic or geometric?

Answer 1

This sequence is geometric because each term is obtained by multiplying the previous term by 1/3. To see this, note that 3/81 = 1/27 is the common ratio between the first two terms, and 1/9 ÷ (3/81) = 1/27 is the common ratio between the second and third terms. Therefore, this sequence is geometric.