Equivalent Fractions (Cambridge O Level Maths)

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Mark

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Equivalent Fractions

How do I find equivalent fractions?

  • “Splitting into 2 parts, then taking 1 part” is the same as “splitting into 4 parts, then taking 2 parts”
    • 1 half is the same as 2 over 4 
    • Similarly,2 over 4 is the same as 4 over 8, or  8 over 16, or 3 over 6 etc
  • Equivalent fractions are two fractions that represent the same amount (they are different ways of writing the same thing)
  • To make equivalent fractions, multiply the top and bottom of a fraction by the same number
    • 5 over 6 is equivalent to fraction numerator 5 cross times 2 over denominator 6 cross times 2 end fraction equals 10 over 12 and fraction numerator 5 cross times 3 over denominator 6 cross times 3 end fraction equals 15 over 18 and fraction numerator 5 cross times 4 over denominator 6 cross times 4 end fraction equals 20 over 24 …etc
    • For each fraction, there are an infinite number of equivalent fractions!

Examiner Tip

  • Using equivalent fractions can help with shading parts of diagrams questions as well as adding and subtracting fractions without a calculator

Simplifying Fractions

How do I simplify fractions?

  • If both the numerator and denominator can be divided by the same number (called a common factor), the fraction can be simplified (made easier)
  • To simplify the fraction, divide the top and bottom by the common factor
    • 12 over 18 equals fraction numerator 12 divided by 6 over denominator 18 divided by 6 end fraction equals 2 over 3
    • 25 over 45 equals fraction numerator 25 divided by 5 over denominator 45 divided by 5 end fraction equals 5 over 9
    • This process is also called cancelling a fraction
    • The simplified fraction is an equivalent fraction
  • A fully simplified fraction is the simplest equivalent fraction that can be made using whole numbers on top and bottom

Examiner Tip

  • Make use of your calculator in the exam if it is available to you
    • typing any fraction into it and pressing equals will automatically simplify the fraction for you
  • If you do not have a calculator check your fraction is simplified by looking for any common factors on the numerator and denominator

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Mark

Author: Mark

Expertise: Maths

Mark graduated twice from the University of Oxford: once in 2009 with a First in Mathematics, then again in 2013 with a PhD (DPhil) in Mathematics. He has had nine successful years as a secondary school teacher, specialising in A-Level Further Maths and running extension classes for Oxbridge Maths applicants. Alongside his teaching, he has written five internal textbooks, introduced new spiralling school curriculums and trained other Maths teachers through outreach programmes.