Lesson plan

7. Sewing Shirts: Use benchmark fractions to solve problems (A)

teaches Common Core State Standards CCSS.Math.Content.5.NF.A.1 http://corestandards.org/Math/Content/5/NF/A/1
teaches Common Core State Standards CCSS.Math.Content.5.NF.A.2 http://corestandards.org/Math/Content/5/NF/A/2
teaches Common Core State Standards CCSS.Math.Practice.MP2 http://corestandards.org/Math/Practice/MP2
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: Use benchmark values of 0, half, and 1 to estimate sums of fractional values, and check estimates with exact calculations.

This lesson provides an opportunity for students to apply their knowledge and understanding of estimation and addition with fractions to a real-life situation. Students are asked to estimate, to the nearest half yard, the amount of fabric for a shirt, then to check the estimate with exact calculations.

Key Concept students will use: 

  • We can use the magnitude of fractions to be added or subtracted to estimate the sum or difference as less than or greater than some whole number, or to tell what two whole numbers the result should fall between.

  • Naming the sum or difference of two fractions as one number requires rewriting the fractions with same size pieces.

Skills students will use:

  • Compare fractional values to benchmarks of 0, half, and 1 (Grade 4, Unit 5)
  • Find equivalent fractions (Grade 3, Unit 10)
  • Add and subtract fractions with different sized pieces (unlike units)

Students engage in Mathematical Practice 2 (Reason Abstractly and Quantitatively) as they use their number sense to reason about the size of fractional values and pause to decide if their answers are reasonable.  They then practice using operations flexibly to check estimates with exact calculations.

Key vocabulary: 

  • estimate
  • sum
  • difference
  • equivalent
  • reasonable

Special materials needed:

  • Students may need fraction tape for intervention.