## 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

# Subtract Across Zero Using Number Lines

Unit 2: Subtraction
Lesson 5 of 5

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

Print Lesson
26 teachers like this lesson
Standards:
Subject(s):
50 minutes

### Diane Siekmann

##### Similar Lessons

###### Mental Math with Place Value
3rd Grade Math » Place Value
Big Idea: It is imperative that students have a strong understanding of place value in order to complete and communicate any given math task. This lesson invites them to re-explore strategies they have created prior to teaching standard algorithms.
Favorites(17)
Resources(14)
Troy, MI
Environment: Suburban

###### Initial Informal Assessments
3rd Grade Math » 1st Week: Getting to Know Each Other Through Graphs
Big Idea: Get to know your students' learning personalities as you observe them on this informal assessment.
Favorites(17)
Resources(12)
Tucson, AZ
Environment: Urban

###### Multi-Digit Subtraction
5th Grade Math » Targeted Skills Interventions
Big Idea: Beg, borrow, steal? I think borrowing is best!
Favorites(10)
Resources(9)
Grand Rapids, MI
Environment: Urban