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?
  
  

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• 1.
  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.
  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.
  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.
  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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