Chapter 9: Problem 54
Write \(0 . \overline{65}\) as an infin te geometric series using summation notation. Then use the formula for fi ding the sum of an infin te geometric series to convert 0.65 to a fraction.
Short Answer
Expert verified
The fraction equivalent to \(0.\overline{65}\) is \(\frac{65}{99}\).
Step by step solution
01
Identify the Repeating Decimal
The decimal number given is \(0.\overline{65}\), which indicates that 65 is the repeating part.
02
Express as an Infinite Sum
Write \(0.\overline{65}\) as an infinite geometric series: \(0.\overline{65} = 0.65 + 0.0065 + 0.000065 + \ldots\).
03
Find the First Term and Common Ratio
In the geometric series, the first term \(a = 0.65\) and the common ratio \(r = 0.01\) because each subsequent term is a multiplication of the previous one by \(0.01\).
04
Use the Formula for Infinite Geometric Series
The sum of an infinite geometric series is given by \(S = \frac{a}{1 - r}\). Substitute \(a = 0.65\) and \(r = 0.01\) into this formula.
05
Calculate the Sum
Substitute the values: \(S = \frac{0.65}{1 - 0.01} = \frac{0.65}{0.99}\).
06
Convert to a Fraction
Calculate \(\frac{0.65}{0.99}\). Simplify by multiplying the numerator and denominator by 100 to get \(\frac{65}{99}\).
07
Final Answer
So, the fraction form of \(0.\overline{65}\) is \(\frac{65}{99}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Repeating Decimal
A repeating decimal is a decimal number where a digit or a group of digits repeats indefinitely. For example, in the number \(0.\overline{65}\), the digits "65" repeat over and over again.
Rewriting a repeating decimal as a series allows us to express it in mathematical forms that are easier to work with, like fractions or sums. In our exercise, \(0.\overline{65}\) is represented as \(0.65 + 0.0065 + 0.000065 + \ldots\) showing a repeating pattern. This illustrates the transition from a repeating decimal into a series.
Rewriting a repeating decimal as a series allows us to express it in mathematical forms that are easier to work with, like fractions or sums. In our exercise, \(0.\overline{65}\) is represented as \(0.65 + 0.0065 + 0.000065 + \ldots\) showing a repeating pattern. This illustrates the transition from a repeating decimal into a series.
Infinite Series
An infinite series is a sum of infinitely many terms. When looking at repeating decimals like \(0.\overline{65}\), they can be expressed as an infinite geometric series.
Using the example of \(0.65 + 0.0065 + 0.000065 + \ldots\), each term represents a smaller contribution adding up to the whole value of the repeating decimal.
Using the example of \(0.65 + 0.0065 + 0.000065 + \ldots\), each term represents a smaller contribution adding up to the whole value of the repeating decimal.
- Each new term is formed by multiplying the previous term by a constant, known as the common ratio \(r\).
- In this case, the series follows a pattern where each term is the previous term multiplied by \(0.01\).
Sum of a Series
Finding the sum of a geometric series, especially an infinite series, allows us to consolidate an endless number of terms into a finite expression.
This is done using the formula for the sum of an infinite geometric series: \[ S = \frac{a}{1-r} \]
This is done using the formula for the sum of an infinite geometric series: \[ S = \frac{a}{1-r} \]
- Here, \(a\) is the first term of the series.
- \(r\) is the common ratio, and must satisfy \(|r| < 1\) for the series to converge.
Fraction Conversion
Converting the sum of a series from a decimal to a fraction ensures precision and a clean numeric representation.
In our example, we need to convert the sum of \(\frac{0.65}{0.99}\) to a fraction. By multiplying the numerator and denominator by 100, to eliminate the decimal point, we get \(\frac{65}{99}\).
In our example, we need to convert the sum of \(\frac{0.65}{0.99}\) to a fraction. By multiplying the numerator and denominator by 100, to eliminate the decimal point, we get \(\frac{65}{99}\).
- This step requires simplifying if possible, though in this case, \(\frac{65}{99}\) is already in simplest form.