Question

A sequence of numbers begins with 12 and progresses geometrically. Each number is the previous number divided by 2.

Which value can be used as the common ratio in an explicit formula that represents the sequence?

One-half
2
6
12

Answer 1

One-half.

Since each term is the previous term divided by 2, the common ratio r = 1/2. The explicit formula is a_n = 12*(1/2)^(n-1).