Chapter 5: Problem 2
Without sigma notation. Then evaluate them. $$\sum_{k=1}^{3} \frac{k-1}{k}$$
Short Answer
Expert verified
The sum is \( \frac{7}{6} \).
Step by step solution
01
Expand the Series without Sigma Notation
First, let's interpret the given sigma notation. The series is the sum of terms of the form \( \frac{k-1}{k} \) where \( k \) ranges from 1 to 3. This means we need to evaluate and sum the following terms: \( \frac{1-1}{1} \), \( \frac{2-1}{2} \), \( \frac{3-1}{3} \).
02
Compute Individual Terms
Next, compute each term individually:- For \( k = 1 \), \( \frac{1-1}{1} = \frac{0}{1} = 0 \).- For \( k = 2 \), \( \frac{2-1}{2} = \frac{1}{2} \).- For \( k = 3 \), \( \frac{3-1}{3} = \frac{2}{3} \).
03
Sum the Terms
Now, sum up the computed terms: \( 0 + \frac{1}{2} + \frac{2}{3} = \frac{0}{1} + \frac{1}{2} + \frac{2}{3} \).
04
Find a Common Denominator for Addition
To add the fractions, find a common denominator. The least common multiple of 2 and 3 is 6. Convert each fraction:- \( \frac{1}{2} = \frac{3}{6} \)- \( \frac{2}{3} = \frac{4}{6} \)Sum: \( 0 + \frac{3}{6} + \frac{4}{6} = \frac{3+4}{6} = \frac{7}{6} \)
05
Simplify the Result if Possible
The fraction \( \frac{7}{6} \) is already in its simplest form.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Sigma Notation
Sigma notation, denoted by the Greek letter \( \Sigma \), is a concise way to express the sum of a sequence of numbers. It's widely used in mathematics to simplify the representation of summation. In this particular exercise, sigma notation is used to describe the series \( \sum_{k=1}^{3} \frac{k-1}{k} \).
Here's a breakdown of the different parts:
Here's a breakdown of the different parts:
- The \( \Sigma \) symbol itself stands for 'sum.'
- Below it, \( k=1 \) specifies the starting value of the index \( k \).
- Above it, \( 3 \) indicates the ending value for \( k \).
- The expression \( \frac{k-1}{k} \) is the formula for each term as \( k \) takes values from 1 to 3.
Fraction Addition
Adding fractions is a fundamental process in arithmetic that requires combining fractions to produce a single result. For the series we are evaluating, the terms involve fractions that need to be summed:
First, compute each term separately:
First, compute each term separately:
- For \( k = 1 \), the term is \( \frac{0}{1} = 0 \).
- For \( k = 2 \), calculate \( \frac{1}{2} \).
- For \( k = 3 \), it's \( \frac{2}{3} \).
Common Denominator
For adding fractions like \( \frac{1}{2} \) and \( \frac{2}{3} \), finding a common denominator is necessary. This means identifying the least common multiple (LCM) of the denominators involved, here 2 and 3.
Steps to find a common denominator:
Steps to find a common denominator:
- The LCM of 2 and 3 is 6. This is the smallest number that both 2 and 3 divide into evenly.
- Convert \( \frac{1}{2} \) to an equivalent fraction with the denominator 6 by finding \( \frac{1 \times 3}{2 \times 3} = \frac{3}{6} \).
- Convert \( \frac{2}{3} \) to \( \frac{2 \times 2}{3 \times 2} = \frac{4}{6} \).