Lesson plan

4. Adding two-digit numbers with strategies (A)

teaches Common Core State Standards CCSS.Math.Content.1.NBT.C.4 http://corestandards.org/Math/Content/1/NBT/C/4
teaches Common Core State Standards CCSS.Math.Practice.MP6 http://corestandards.org/Math/Practice/MP6
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Lesson objective: Add two-digit and one-digit numbers together using the strategy of composing a new ten when necessary. 

This lesson provides an opportunity for students to apply their knowledge and understanding of place value to add numbers in a real-life situation. Students are asked to find the total number of books being packed into each box as the teacher organizes her classroom library. 

Key Concept students will use: 

  • When adding two-digit numbers, we add tens with tens and ones with ones (sometimes composing a ten). 

Skills students will use:

  • place value knowledge to identify tens and ones (Grade 1, Unit 8) 
  • strategies for adding two-digit numbers (Grade 1, Unit 11) 
  • decomposing to add more efficiently  (Grade 1, Unit 11)

Students engage in Mathematical Practice 6 (Attend to Precision) as they decompose and combine numbers to make a new ten.  Students may use base ten blocks, ten frames or a series of equations to show their steps for adding.  Students will strategically decide how to decompose a single-digit number to combine the addends in steps that use multiples of ten.

Key vocabulary: 

  • compose
  • decompose
  • ones
  • sum
  • tens

Special materials needed:

  • base ten blocks (optional)
  • ten frames (optional)