Math  /  Algebra

QuestionEvaluate the infinite geometric series: 1+1/5+1/25+1+1 / 5+1 / 25+\ldots
1 2 3
65/27 5/4 9/59 / 5 5/6

Studdy Solution

STEP 1

1. The series is an infinite geometric series.
2. The first term of the series is a=1 a = 1 .
3. The common ratio r r can be determined from the series.

STEP 2

1. Identify the first term and the common ratio.
2. Use the formula for the sum of an infinite geometric series.
3. Calculate the sum.

STEP 3

Identify the first term a a and the common ratio r r .
The first term a a is the first term of the series:
a=1 a = 1
The common ratio r r is the ratio of the second term to the first term:
r=1/51=15 r = \frac{1/5}{1} = \frac{1}{5}

STEP 4

Use the formula for the sum S S of an infinite geometric series, which is valid when r<1 |r| < 1 :
S=a1r S = \frac{a}{1 - r}
Substitute the values of a a and r r into the formula:
S=1115 S = \frac{1}{1 - \frac{1}{5}}

STEP 5

Simplify the expression for the sum:
S=1115=145 S = \frac{1}{1 - \frac{1}{5}} = \frac{1}{\frac{4}{5}}
S=1×54=54 S = \frac{1 \times 5}{4} = \frac{5}{4}
The sum of the infinite geometric series is:
54 \boxed{\frac{5}{4}}

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