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3.8 Common denomination: more adding and subtracting


Created on 21 August 2019 by ncetm_administrator
Updated on 22 August 2019 by ncetm_administrator

Introduction

Learn to add and subtract fractions with different denominators by first finding a common denominator. Compare fractions using a range of methods, including converting to a common denominator.

Teaching points

  • Teaching point 1: In order to add related fractions, first convert one fraction so that both share the same denominator (a ‘common denominator’).
     
  • Teaching point 2: To subtract related fractions, first convert one fraction so that both share a common denominator.
     
  • Teaching point 3: The common denominator method can be extended to adding and subtracting non unit related fractions.
     
  • Teaching point 4: To add and subtract non-related fractions, the product of the two denominators provides a common denominator.
     
  • Teaching point 5: Converting to common denominators is one of several methods that can be used to compare fractions.
     

 
 

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