# Is it Postive or Negative?

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## Objective

SWBAT determine if a sum or difference will be positive or negative using various models.

#### Big Idea

Students will internalize the rules for integer addition by discovering patterns.

## Intro & Rationale

The purpose of this lesson is to engage students in the practice of argumentation. The warm up illustrates the use of a number line as evidence to support the solution. The sorting activity provides opportunities for students to dissagree and argue about the solutions. Students must use explanations and/or mathematical models to support their reasoning. (mp 3)Their evidence and explanations may include reference to the hot & cold cube context learned in earlier lessons (Mathmaster Chef series), number line, or plus (+) and minus (-) symbols. (mp 4) I remind students that their modeling and explanations are useful not only in convincing their peers, but also are helpful in convincing themselves during a test. Evidence can be used to help them decide how to solve or figure something out just as it can be used to convince someone else of the solution. (mp1)

## Warm up

15 minutes

The Warm up asks students to solve the following problems and asks what they would look like on a number line:

• -20 + 10
• -10 - (-5)
• 5 - (-10)
• -3 x (-10)

As we go over the Warm up notes I draw the open number line for each problem to emphasize that subtracting negatives moves in the positive direction on the number line in order to reinforce the idea of adding the opposite. Not only does this help them visualize the math, but it also helps familiarize them with a tool they can use to help them explain and support their results. This helps them later use the appropriate tools as evidence during argumentation (mp3 & 5)

## Exploration

30 minutes

Students work collaboratively in pairs or trios to sort the integer operation sort cards.docx into two categories. They need to group the problems according to whether the solution will be positive or negative. This is a good way to engage students in argumentation and to encourage the use of mathematical modeling and explanation to support their reasoning. (mp3)