A) 3
B) 6
C) 9
D) 12
Correct Answer: D
Solution :
It is an arithmetico-geometric series \[{{S}_{\infty }}=\frac{a}{1-r}+\frac{dr}{{{(1-r)}^{2}}}\]\[=\frac{1}{1-\frac{1}{2}}+\frac{2}{{{\left( 1-\frac{1}{2} \right)}^{2}}}\]\[=\frac{2}{\frac{1}{2}}+\frac{2}{\frac{1}{4}}\] \[=4+8=12\].
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