Answer:
Option A. 5
Explanation:
From the question given above, the following data were obtained:
First term (a) = –3
Common ratio (r) = 6
Sum of series (Sₙ) = –4665
Number of term (n) =?
The number of terms in the series can be obtained as follow:
Sₙ = a[rⁿ – 1] / r – 1
–4665 = –3[6ⁿ – 1] / 6 – 1
–4665 = –3[6ⁿ – 1] / 5
Cross multiply
–4665 × 5 = –3[6ⁿ – 1]
–23325 = –3[6ⁿ – 1]
Divide both side by –3
–23325 / –3 = 6ⁿ – 1
7775 = 6ⁿ – 1
Collect like terms
7775 + 1 = 6ⁿ
7776 = 6ⁿ
Express 7776 in index form with 6 as the base
6⁵ = 6ⁿ
n = 5
Thus, the number of terms in the geometric series is 5.