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What is the value of \(1 + \frac{1}{4} + \frac{1}{{16}} + \frac{1}{{64}} + \frac{1}{{256}} + \ldots ?\)
1. 2
2. \(\frac{7}{4}\)
3. \(\frac{3}{2}\)
4. \(\frac{4}{3}\)

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Correct Answer - Option 4 : \(\frac{4}{3}\)

Concept:

For a GP of the form:

a + ar + ar2 + ar3 +…..

The sum is given by:

\(Sum= \frac{a}{{1 - r}}\)

Calculation:

The given sequence is

\(x\left( n \right) = 1 + \frac{1}{4} + \frac{1}{{16}} + \frac{1}{{64}} + \frac{1}{{256}} + \ldots\)

\(= 1 + \frac{1}{{{2^2}}} + \frac{1}{{{2^4}}} + \frac{1}{{{2^6}}} + \frac{1}{{{2^8}}} + \ldots \)

The series is GP series with:

a = 1

\(r = \frac{1}{{{2^2}}} = \frac{1}{4}\)

Sum of the infinite series will be:

\(Sum= \frac{a}{{1 - r}}\)

\(= \frac{1}{{1 - \frac{1}{4}}} = \frac{1}{{\frac{3}{4}}}\)

\(= \frac{4}{3}\)

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