What's up with that? The Connection Between Addition and Subtraction of Integers

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Objective

SWBAT explain the relationship between addition and subtraction of integers by using counters and zero pairs.

Big Idea

Students use integer chips to understand the abstract connection between addition, subtraction, and the additive inverse.

Do Now

6 minutes

Students enter silently. They will all have their journals on their desks. Many have been falling behind during the opening part of class in the last two weeks and will get an opportunity to complete missing journal entries. Those who are finished with their journal entry will work on an operations puzzle that allows for the opportunity to earn achievement points. As students complete each puzzle, they may raise their hands to have their work checked and earn stars on their achievement card. After 5 minutes all students will be asked to turn in their homework form the weekend and get ready for the task.

20 minutes

Essential Question: How is subtracting signed numbers related to adding signed numbers?

As we move through examples, I ask student volunteers to take turns at the document camera to display their model and draw their representation. Students continue with examples #4-9.  I encourage students to speak with their neighbor and share out as a classif they are noticing a relationship between addition and subtraction. If any student gives an explanation that is too vague or broad, I offer counter examples and ask them to continue to think about the relationship (i.e. student states, “addition and subtraction are the same”, teacher responds, “what do you mean they are the same? So 9-5 is the same as 9+5? How are they the same?”). If a student words something in a succinct and mathematically correct way, we ask the student to repeat what he stated so that we can write it in our journals. I write it on a sheet of paper and project it on the document camera.