Jambmaths question:
Find the sum to infinity $\tfrac{1}{2},\tfrac{1}{6},\tfrac{1}{18}---$
Option A:
$\tfrac{2}{3}$
Option B:
$\tfrac{1}{3}$
Option C:
$\tfrac{3}{4}$
Option D:
1
Jamb Maths Solution:
$\begin{align} & {{S}_{\infty }}=\frac{a}{1-r} \\ & a=\frac{1}{2},\text{ }r=\frac{\tfrac{1}{6}}{\tfrac{1}{2}}=\frac{1}{3} \\ & S\infty =\frac{\tfrac{1}{2}}{1-\tfrac{1}{3}}=\frac{\tfrac{1}{2}}{\tfrac{2}{3}}=\frac{1}{2}\times \frac{3}{2}=\frac{3}{4} \\\end{align}$
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