Reflection: Connection to Prior Knowledge Subtract Across Zero Using Number Lines - Section 2: Using A Number Line


Because the open number line is so important not only for students to demonstrate thinking but also because it develops their conceptual understanding, I spend a great deal of time practicing addition and subtraction without regrouping on number lines.

Some of my students had only used a labeled number line labeled (0-20) that was part of their name tag in second grade.  Some of my students had never used a number line, which is why I spent time modeling and thinking with it in this section of the lesson.  

Another important skill the students need is skip counting, starting at random locations, and increasing and decreasing numbers by ones and tens.  For example, the students need to be able to identify one more and less than 36, and ten more and less than 36.  In third grade, students should be able to apply this skill to hundreds and thousands as well.  

During this lesson I discovered a group of students that had not used number lines and lacked counting skills and familiarity with a hundreds chart, and I worked with these students separately on these skills.  This lesson was beyond their current knowledge, and they were frustrated by what was being presented in this lesson. 

  Connect to Prior Knowledge
  Connection to Prior Knowledge: Connect to Prior Knowledge
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Subtract Across Zero Using Number Lines

Unit 2: Subtraction
Lesson 5 of 5

Objective: SWBAT use blank number lines and place value to subtract across zeros.

Big Idea: Using a number line to subtract across zeros supports students conceptual understanding of crossing decades when subtracting.

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