Adding and subtracting fractions with unlike denominators

Lessons

• Introduction
  a)

  Simplify fractions: Method A - By using greatest common factors
  
  
  b)

  Simplify fractions: Method B - By using common factors
  
  
  c)

  What are equivalent fractions?
  
  
  d)

  How to add fractions?
  
  
  e)

  How to subtract frations?
  • subtracting with improper fractions
  • subtracting with mixed numbers
  
  

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• 1.
  Determine the Lowest Common Denominator of Two Fractions
  Determine the lowest common denominator (LCD) for the pair of fractions using multiples.
  a)

  $\frac{2}{4},\frac{1}{8}$
  
  
  b)

  $\frac{8}{11},\frac{7}{33}$
  
  
  c)

  $\frac{4}{6},\frac{5}{9}$
  
  

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• 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.
  a)

  $\frac{7}{12},\frac{2}{4}$
  
  
  b)

  $\frac{1}{2},\frac{1}{3}$
  
  
  c)

  $\frac{8}{10},\frac{8}{15}$
  
  

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• 3.
  Word Problems: Adding And Subtracting Fractions With Unlike Denominators
  Calculate using the four square method. Write the answer in the lowest terms.
  a)

  $\frac{3}{6}+\frac{1}{4}$
  
  
  b)

  $\frac{4}{5}-\frac{1}{3}$
  
  
  c)

  $\frac{2}{3}+\frac{2}{10}$
  
  
  d)

  $\frac{8}{10}-\frac{32}{80}$
  
  

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• 4.
  Word Problems: Adding And Subtracting Fractions With Unlike Denominators
  A cargo ship was $\frac{1}{8}$ full of food containers and $\frac{2}{4}$ full of furniture. How much space was left?

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• 5.
  Kate baked a tray of muffins for her two friends, Mary and Stephanie. Mary ate $\frac{1}{3}$ of the muffins and Stephanie ate $\frac{3}{6}$ of the muffins. What fraction of the muffins did the two friends eat in total?

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