Lesson plan

Insect Olympics: Add and subtract fractions in a word problem

teaches Common Core State Standards CCSS.Math.Content.4.NF.B.3a http://corestandards.org/Math/Content/4/NF/B/3/a
teaches Common Core State Standards CCSS.Math.Content.4.NF.B.3b http://corestandards.org/Math/Content/4/NF/B/3/b
teaches Common Core State Standards CCSS.Math.Content.4.NF.B.3d http://corestandards.org/Math/Content/4/NF/B/3/d
teaches Common Core State Standards CCSS.Math.Practice.MP3 http://corestandards.org/Math/Practice/MP3
teaches Common Core State Standards CCSS.Math.Practice.MP4 http://corestandards.org/Math/Practice/MP4
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Lesson objective: Add and subtract fractions in a word problem.

This lesson provides an opportunity for students to apply their knowledge and understanding of fraction addition and subtraction to a real-life situation. Students are asked to draw a diagram of an obstacle course for the Insect Olympics using a description. The distance of one segment of the course is not revealed, so students must use addition and subtraction strategies to accurately model it.

Key Concept students will use: 

  • Fractions can be decomposed into combinations of unit and non-unit fractions because the length a/b on the number line is determined by a lengths of 1/b from 0, and this occurs infinitely many times
  • Addition and subtraction have the same meaning when used with fractions as when used with whole numbers 

Skills students will use:

  • Adding fractions with like denominators
  • Subtracting fractions with like denominators

Students engage in Mathematical Practice S.MP.4. (Model with mathematics) by using a description to create a model of a real-world situation, and then using that model to answer question about the situation. The number line is especially important in this lesson as students use it to show the distance between the obstacles.

Key vocabulary: 

  • equal
  • number line