Question

If the first two terms of a geometric sequence are a1=216 and a2=72 then which of the following is the third term, a3=?

Explain how you did it please
1)648
2)24
3)360
4)12

Answer 1

(2) 24

Explanation:

The common ratio r of a geometric sequence is

`(a_(2) )/(a_(1) )` =
`(72)/(216)` =
`(1)/(3)`

To find the next term in the sequence multiply the previous term by r

`a_(3)` = 72 ×
`(1)/(3)` = 24 → (2)