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Getting to know the counting, addition and subtraction math lesson

This lesson provides an open number line virtual manipulative for teachers to use within a variety of instructional contexts. Note that in contrast to number lines where all the counting numbers are shown, the open number line only shows the result of operations. Teachers can use it to represent student strategies such as skip counting, adding on, removing, or difference. Research shows it helps students move away from counting one-by-one.1

Getting to know the manipulative

The open number line supports students in envisioning numbers:

• As the magnitude of distances on a line
• As equivalent quantities
• By their proximity to landmark numbers

They are also able to explore operations (addition, subtraction, etc.) on the open number line to support the development of various efficient strategies for computational fluency.

Professional development ideas

• Use the open number line to skip count.
  • Invite students to share patterns they notice.
  • Challenge students to use a pattern to predict the next endpoint.
  • Vary the activity by starting at numbers other than zero or counting backwards.
• Use the open number line to model a situation.
  • Whether it’s a situation that comes up during a math lesson or a question that arises when students are on a field trip, the open number line can be used to model a number of mathematical situations.
• Use the open number line to model students’ strategies during mini-lessons using strings of related problems.2
  • Invite students to share how their strategy is similar to or different than another strategy. Use the open number line to highlight the similarities and differences.
  • Save a snapshot or copy of the screen using the student’s name and date. This is a nice piece of evidence that can be used in a student’s file or shared with parents.