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      Checking understanding of addition and subtraction with fractions

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      Lesson details

      Learning outcome

      I can use the mathematical structures that underpin the addition and subtraction of fractions.

      Key learning points

      1. The denominators of each fraction should split the whole into the same number of equal pieces.
      2. The numerators are added or subtracted.
      3. The size of each piece has not changed so the denominator does not change.

      Keywords

      • Numerator - The expression in a fraction that is written above the fraction line. It is the dividend.

      • Denominator - The expression in a fraction that is written below the fraction line. It is the divisor.

      • Proper fraction - A proper fraction is a fraction where the numerator is less than the denominator.

      • LCM - LCM is an abbreviation for lowest common multiple.

      Common misconception

      Simply adding or subtracting the numerators and denominators.

      Emphasise that the denominator tells us the name of the unit. In order to add or subtract things they must have a common name.

      Teacher tip

      Confidence with equivalent fractions is key in this lesson. Use mini whiteboards and ask students to write down as many equivalent fractions as they can. You could give them a pair of fractions and decide which is most useful for combining them.

      Licence

      This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0
       except where otherwise stated. See Oak's terms & conditions
       (Collection 2).

      Lesson video

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      Prior knowledge starter quiz

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      6 Questions

      Q1.
      What is the word for the number above the fraction line?

      Correct Answer: numerator

      Q2.
      Which of the following are equivalent to $${2}\over{3}$$?

      Correct answer: $${4}\over{6}$$
      $${8}\over{10}$$
      Correct answer: $${10}\over{15}$$
      Correct answer: $${14}\over{21}$$
      $${24}\over{35}$$

      Q3.
      Calculate $${2}\over{7}$$ + $${4}\over{7}$$.

      $${2}\over{7}$$
      $${3}\over{7}$$
      Correct answer: $${6}\over{7}$$
      $${8}\over{7}$$

      Q4.
      Calculate $${6}\over{7}$$ - $${3}\over{7}$$.

      $${1}\over{7}$$
      $${2}\over{7}$$
      Correct answer: $${3}\over{7}$$
      $${4}\over{7}$$

      Q5.
      The larger the denominator, the the parts.

      Correct Answer: smaller

      Q6.
      Sort the following from smallest to largest.

      1 - $${1}\over{20}$$
      2 - $${1}\over{13}$$
      3 - $${1}\over{9}$$
      4 - $${1}\over{5}$$
      5 - $${1}\over{3}$$

      Assessment exit quiz

      Download exit quiz questions (PDF)

      6 Questions

      Q1.
      The most efficient way to add or subtract fractions is using the .

      HCF
      Correct answer: LCM
      same denominator
      doing the same to the top and bottom

      Q2.
      Which of the following is not a common denominator of $${1}\over{4}$$ and $${7}\over{12}$$?

      Correct answer: 2
      12
      36
      120

      Q3.
      $$\frac{2}{7} + \frac{1}{8} \square \frac{2}{7} + \frac{1}{9}$$

      Correct answer: >
      <
      =

      Q4.
      Calculate $${5}\over{12}$$ - $${1}\over{4}$$.

      $${4}\over{8}$$
      Correct answer: $${2}\over{12}$$
      $${3}\over{12}$$
      $${4}\over{12}$$

      Q5.
      Which of the following is not a correct alternative for $${1}\over{4}$$ - $${5}\over{8}$$ + $${3}\over{16}$$?

      $${1}\over{4}$$ + $${3}\over{16}$$ - $${5}\over{8}$$
      Correct answer: $${1}\over{4}$$ - $$\left(\frac{5}{8} + \frac{3}{16}\right)$$
      $${1}\over{4}$$ + $${3}\over{16}$$ + $$\left(-\frac{5}{8}\right)$$

      Q6.
      Calculate $${1}\over{4}$$ - $${5}\over{8}$$ + $${3}\over{16}$$?

      $$\left(-\frac14\right)$$
      $$\left(-\frac2{16}\right)$$
      Correct answer: $$\left(-\frac3{16}\right)$$
      $$\left(-\frac9{16}\right)$$

      To help you plan your 7 maths lesson on: Checking understanding of addition and subtraction with fractions, download all teaching resources for free and adapt to suit your pupils' needs...