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Activity: Classifying mental subtractions

This page contains examples showing how students subtract mentally. Usually these problems would be done without any writing, but the movies and adult voice are used here to explain what has been done. The examples demonstrate a great variety of methods.

Watch the following movies and classify each according to the method used. Select from the list on the right.

Click on the linked 'comments' to check your answers.

 

click here for explanations of the classifications >>>

  Classifications
  complementary addition
  subtraction in stages
  rounding
  equal additions principle
  renaming principle
  other methods

Amy

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Ann

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Ben

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Fikeni

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Jim

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Loretta

  movie link
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Mary

movie link
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Nina

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Peter

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Sam

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Sunil

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Tess

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