Lesson plan

11. Understand comparison problems to find the unknown. (C)

teaches Common Core State Standards MP1 http://corestandards.org/Math/Practice/MP1
teaches Common Core State Standards MP7 http://corestandards.org/Math/Practice/MP7
teaches Common Core State Standards 2.OA.A.1 http://corestandards.org/Math/Content/2/OA/A/1
teaches Common Core State Standards 2.OA.B.2 http://corestandards.org/Math/Content/2/OA/B/2

11. Understand comparison problems to find the unknown. (C)

Lesson objective: Understand how to use addition and subtraction in compare word problems to find the unknown.

Students bring prior knowledge of comparing numbers from 1.OA.A.1 This prior knowledge is extended to explaining what comparison situations mean as students explore the relationship between addition and subtraction. A conceptual challenge students may encounter is understanding the comparison language. 

The concept is developed through work with part/part/whole models and counters, which allow students to compare values and see the relationship among the values using addition and/or subtraction.

This work helps students deepen their understanding of numbers and operations. By comparing two values using words such as more than, less than, and fewer than, students understand how these values are related.

Students engage in Mathematical Practice 1 (Make sense of problems and persevere in solving them) as they notice that they can use the properties of operations and the relationship between addition and subtraction to solve comparison situations using the number line. Students also engage in Mathematical Practice 7 (Look for and make use of structure) as they utilize their knowledge of number sequence when comparing two numbers using “more” and “less" than.

Key vocabulary:

  • addend
  • addition
  • compare
  • comparison 
  • equation 
  • fewer than
  • less than
  • missing value
  • more
  • subtraction
  • unknown
  • value

Special materials needed:

  • counters
  • part/part/whole mats