Classify the following set of numbers by determining which of the options is true.

3, 1, 1/3
, 1/9
, 1/27
, . . .

Option #1: The set is an arithmetic sequence.

Option #2: The set is a geometric sequence.

Option #3: The set is some other type of sequence.

Option #4: The set is not a sequence.

(1 point)
The true statement is Option #

1 answer

To classify the given set of numbers:

3, 1, 1/3, 1/9, 1/27, ...

We should first analyze the relationship between the consecutive terms.

  1. Determine the ratio between consecutive terms:
    • From 3 to 1: \( \frac{1}{3} \)
    • From 1 to \( \frac{1}{3} \): \( \frac{1/3}{1} = \frac{1}{3} \)
    • From \( \frac{1}{3} \) to \( \frac{1}{9} \): \( \frac{1/9}{1/3} = \frac{1/9 \cdot 3}{1} = \frac{1}{3} \)
    • From \( \frac{1}{9} \) to \( \frac{1}{27} \): \( \frac{1/27}{1/9} = \frac{1/27 \cdot 9}{1} = \frac{1}{3} \)

In each case, we see that each term is obtained by multiplying the previous term by \( \frac{1}{3} \).

  1. Definition check:
    • An arithmetic sequence involves adding a constant difference to each term (e.g., 2, 4, 6).
    • A geometric sequence involves multiplying each term by a constant ratio (e.g., 2, 4, 8).

Since the ratio between each term is constant (\( \frac{1}{3} \)), we find that this set is a geometric sequence.

Thus, the correct option is: Option #2: The set is a geometric sequence.