Find the sum of the first five terms of the G P... - WAEC Mathematics 1990 Question
Find the sum of the first five terms of the G.P 2,6, 18 ....
A
484
B
243
C
242
D
130
correct option: c
\(S_{n} = \frac{a(r^n - 1)}{r - 1}\)
a = 2; r = 6/2 = 3.
\(S_{5} = \frac{2(3^5 - 1)}{3 - 1}\)
= \(243 - 1 = 242\)
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