How many terms of the series 3 -6 12 24 are nee... - JAMB Mathematics 2006 Question
How many terms of the series 3, -6, 12, 24,... are needed to make a total of 1 - 28?
A
9
B
8
C
12
D
10
correct option: b
Sn = \(\frac{a(1 - (r)^n)}{1 - r}\)
255 = \(\frac{3(1 - (-2))^n}{1 - (2)}\)
255 = \(\frac{3(1-(-2)^n}{3}\)\)
2n = 256
2n = 28
n = 8
255 = \(\frac{3(1 - (-2))^n}{1 - (2)}\)
255 = \(\frac{3(1-(-2)^n}{3}\)\)
2n = 256
2n = 28
n = 8
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