Answer:
a(4) = 15/4
Explanation:
Here we're told that the first term is a(1) = 30 and that the common factor r = 1/2.
Thus, the geometric sequence formula specific to this case is
a(n) = 30(1/:2)^(n-1).
What is the fourth term? Let n = 4,
a(4) = 30(1/2)^(4-1), or a(4) = 30(1/2)^(3), or a(4) = 30(1/8) = 30/8, or, in reduced form,
a(4) = 15/4.