Adding and subtracting fractions with unlike denominators

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Intros
Lessons
  2. Simplify fractions: Method A - By using greatest common factors
  3. Simplify fractions: Method B - By using common factors
  4. What are equivalent fractions?
  5. How to add fractions?
  6. How to subtract frations?
    • subtracting with improper fractions
    • subtracting with mixed numbers
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Examples
Lessons
  1. Determine the Lowest Common Denominator of Two Fractions
    Determine the lowest common denominator (LCD) for the pair of fractions using multiples.
    1. 24,18\frac{2}{4},\frac{1}{8}
    2. 811,733\frac{8}{11},\frac{7}{33}
    3. 46,59\frac{4}{6},\frac{5}{9}
  2. Evaluate Equivalent Fractions Using the Lowest Common Denominator
    Determine the lowest common denominator (LCD) for the pair of fractions using multiples. Then, determine equivalent fractions for the pair of fractions using the LCD.
    1. 712,24\frac{7}{12},\frac{2}{4}
    2. 12,13\frac{1}{2},\frac{1}{3}
    3. 810,815\frac{8}{10},\frac{8}{15}
  3. Word Problems: Adding And Subtracting Fractions With Unlike Denominators
    Calculate using the four square method. Write the answer in the lowest terms.
    1. 36+14\frac{3}{6}+\frac{1}{4}
    2. 45−13\frac{4}{5}-\frac{1}{3}
    3. 23+210\frac{2}{3}+\frac{2}{10}
    4. 810−3280\frac{8}{10}-\frac{32}{80}
  4. Word Problems: Adding And Subtracting Fractions With Unlike Denominators
    A cargo ship was 18\frac{1}{8} full of food containers and 24\frac{2}{4} full of furniture. How much space was left?
    1. Kate baked a tray of muffins for her two friends, Mary and Stephanie. Mary ate 13\frac{1}{3} of the muffins and Stephanie ate 36\frac{3}{6} of the muffins. What fraction of the muffins did the two friends eat in total?
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      Practice
      Topic Notes
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      In this section, we will learn how to add and subtract fractions with unlike denominators. First, we will practice finding the lowest common denominator for a pair of fractions by determining the lowest common multiple of the denominators. The divisibility rules learned in previous section can be used to find the multiples of our denominators. Next, we will practice writing equivalent fractions. When writing equivalent fractions with common denominators, the numerator and denominator in each fraction are both multiplied by the same number. As shown in sections on adding/subtracting fractions with like denominators, we will write our answers in lowest terms by first finding the greatest common factor (GCF) of both the numerator and denominator in our equivalent fraction and then dividing both the numerator and denominator by this GCF.

      In this lesson, we will learn:

      • Determine the Lowest Common Denominator of Two Fractions
      • Evaluate Equivalent Fractions Using the Lowest Common Denominator
      • Add and Subtract Fractions With Unlike Denominators
      • Word Problems: Adding And Subtracting Fractions With Unlike Denominators
      • Challenging: Add and Subtract Fractions With Unlike Denominators
      Basic Concepts
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      Related Concepts
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