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# Adding Fractions Test #3

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In this section, we learn how to add and subtract fractions. For this topic, we will have two different scenarios:

• Adding & Subtracting Fractions with a Common Denominator

• Adding & Subtracting Fractions without a Common Denominator

Adding & Subtracting Fractions with a Common Denominator:

-Place the result over the common denominator

$$\frac{6}{12}$$ -Simplify $$\frac{6}{12} = \frac{2 \cdot 3}{2 \cdot 2 \cdot 3}$$ $$\require{cancel}\frac{\cancel{2} \cdot \cancel{3}}{2 \cdot \cancel{2} \cdot \cancel{3}} = \frac{1}{2}$$ Adding & Subtracting Fractions without a Common Denominator:

Example 1: Find each difference $$\frac{1}{3} - \frac{2}{7}$$ -LCD = LCM(3,7) = 21

-Rewrite each as an equivalent fraction with 21 as the denominator:

$$\frac{1}{3} \cdot \frac{7}{7} = \frac{7}{21}$$ $$\frac{2}{7} \cdot \frac{3}{3} = \frac{6}{21}$$ -Subtract the numerators: 7 - 6 = 1

-Place the result over the common denominator

$$\frac{1}{21}$$ -The fractions is already simplified $$\frac{1}{3} - \frac{2}{7} = \frac{1}{21}$$

• Adding & Subtracting Fractions with a Common Denominator

• Adding & Subtracting Fractions without a Common Denominator

Adding & Subtracting Fractions with a Common Denominator:

- Perform the given operation with the numerators - Add or Subtract the Numerators of the Fractions
- Place the result over the common denominator
- Simplify (reduce the fraction to lowest terms)

-Place the result over the common denominator

$$\frac{6}{12}$$ -Simplify $$\frac{6}{12} = \frac{2 \cdot 3}{2 \cdot 2 \cdot 3}$$ $$\require{cancel}\frac{\cancel{2} \cdot \cancel{3}}{2 \cdot \cancel{2} \cdot \cancel{3}} = \frac{1}{2}$$ Adding & Subtracting Fractions without a Common Denominator:

- Write equivalent fractions with the LCD as each denominator
- Perform the given operation with the numerators - Add or Subtract the Numerators of the Fractions
- Place the result over the common denominator
- Simplify (reduce the fraction to lowest terms)

Example 1: Find each difference $$\frac{1}{3} - \frac{2}{7}$$ -LCD = LCM(3,7) = 21

-Rewrite each as an equivalent fraction with 21 as the denominator:

$$\frac{1}{3} \cdot \frac{7}{7} = \frac{7}{21}$$ $$\frac{2}{7} \cdot \frac{3}{3} = \frac{6}{21}$$ -Subtract the numerators: 7 - 6 = 1

-Place the result over the common denominator

$$\frac{1}{21}$$ -The fractions is already simplified $$\frac{1}{3} - \frac{2}{7} = \frac{1}{21}$$

Adding Fractions Resources:

Videos:

Khan Academy - Video
Khan Academy - Video
Math Antics - Video
Text Lessons:

Math is Fun - Text Lesson
AAA Math - Text Lesson
Purple Math - Text Lesson
Worksheets:

Super Teacher - Worksheet
Khan Academy - Practice
Khan Academy - Practice
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