What is the common ratio in the following geometric sequence?

2, 1/2, 1/8, 1/32, . . .

(1 point)
Responses

1/4
Start Fraction 1 over 4 End Fraction

−1.5
negative 1.5

4
4

1/2

1 answer

In a geometric sequence, the common ratio can be found by dividing any term by the preceding term.

Let's find the common ratio using the first two terms of the given sequence:

  1. First term (a_1): 2
  2. Second term (a_2): \( \frac{1}{2} \)

The common ratio \( r \) can be calculated as follows:

\[ r = \frac{a_2}{a_1} = \frac{\frac{1}{2}}{2} = \frac{1}{2} \times \frac{1}{2} = \frac{1}{4} \]

Now, let's verify this by calculating the ratio between another pair of terms.

Using the third and second terms:

  1. Second term (a_2): \( \frac{1}{2} \)
  2. Third term (a_3): \( \frac{1}{8} \)

\[ r = \frac{a_3}{a_2} = \frac{\frac{1}{8}}{\frac{1}{2}} = \frac{1}{8} \times \frac{2}{1} = \frac{2}{8} = \frac{1}{4} \]

Using the fourth and third terms:

  1. Third term (a_3): \( \frac{1}{8} \)
  2. Fourth term (a_4): \( \frac{1}{32} \)

\[ r = \frac{a_4}{a_3} = \frac{\frac{1}{32}}{\frac{1}{8}} = \frac{1}{32} \times \frac{8}{1} = \frac{8}{32} = \frac{1}{4} \]

In each case, we find that the common ratio \( r \) is consistently \( \frac{1}{4} \).

Therefore, the common ratio of the sequence is:

Start Fraction 1 over 4 End Fraction \( \frac{1}{4} \)