Question

6.(08.04)
What is the sum of the geometric sequence 2, 8, 32, ... if there are 8 terms?

Answer 1

43,690.

Explanation:

The common ratio r is 8/2 = 32/8 = 4.

Sum of n terms = a1 * (r^n - 1) / (r - 1).

a1 = 2 and r = 4 so

Sum of 8 terms = 2 *(4^8 - 1) / (4 - 1)

= 2 * 65535 / 3

= 43,690.