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Evaluate: 1+12+14+18+116+⋯\text{ } 1 +\frac{1}{2} + \frac{1}{4} + \frac{1}{8} + \frac{1}{16} + \cdots 1+21​+41​+81​+161​+⋯​
Question

Evaluate: 1+12+14+18+116+\text{ } 1 +\frac{1}{2} + \frac{1}{4} + \frac{1}{8} + \frac{1}{16} + \cdots

A.

2

B.

1/50

C.

1/22

D.

3

Correct option is A

Given:

 1+12+14+18+116+\text{ } 1 +\frac{1}{2} + \frac{1}{4} + \frac{1}{8} + \frac{1}{16} + \cdots

Formula  Used:

Sum of terms in an infinite GP  = a(1r)\frac{a}{(1-r)} ​​

Solution:

 1+12+14+18+116+\text{ } 1 +\frac{1}{2} + \frac{1}{4} + \frac{1}{8} + \frac{1}{16} + \cdots

This is GP series 

a = 1 , r = 12\frac{1}{2} ​​

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

1(11/2)\frac{1}{(1-1/2)}

= 2 

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