Find the sum of the indicated terms of the geometric sequence.
6,18,54 ...(to 8 terms)

A)s = 19,686
B)s = 19,692
C)s = 19,680
D)s = 19,674
E)none of the above

Question

Find the sum of the indicated terms of the geometric sequence. ​
6,18,54 ...(to 8 terms)
​
A)s = 19,686
B)s = 19,692
C)s = 19,680
D)s = 19,674
E)none of the above

Quizplus · Accepted Answer

The given geometric sequence has a common ratio of 3:
6 x 3 = 18
18 x 3 = 54
and so on.

Using the formula for the sum of the first n terms of a geometric sequence, we have:

s = a(1 - r^n) / (1 - r)

where:
a = first term = 6
r = common ratio = 3
n = number of terms = 8

Plugging in the values, we get:

s = 6(1 - 3^8) / (1 - 3)
s = 6(-6561) / (-2)
s = 19,680

Therefore, the answer is choice C.

Find the Sum of the Indicated Terms of the Geometric