which explains why the sequence 216, 12, 2/3,... is arithmetic or geometric

The sequence 216, 12, 2/3,… is geometric. A geometric sequence is a sequence of numbers in which each term after the first is obtained by multiplying the previous term by a fixed number called the common ratio. In this sequence, each term is obtained by multiplying the previous term by 1/18, which is a fixed number. Therefore, this sequence is geometric.