The purpose of this activity is for students to represent addition and subtraction equations on a number line. Students consider where to begin and in which direction to draw their arrows in order to accurately represent the operation in the given equation. Throughout the activity, encourage students to explain how they know their representation matches the equation. Listen for the ways students explain how they know where to start and end their arrow, which direction they draw their arrow, and how they connect the length of the jump to the equation (MP3).

• “Will you please explain your representation?”
• “How did you decide where to start or end on the number line? How did you decide which direction to draw your arrow?”

• Display the equation and blank number line for .
• Invite previously selected students to share how they represented the equation on the number line.
• Consider asking:
  • “How do you see each number in the equation in _____’s representation?”
  • “How do you know _____’s representation matches the operation (addition or subtraction)?”
• As time permits, continue with the other equations.

The purpose of this activity is for students to write addition and subtraction equations to match number line representations. Students determine the operation represented by looking at the direction of the arrow. They identify the starting number, the length of the jump, and the ending number in order to write the equation. Each representation shows a relationship between the same three numbers. When students explain to each other why they think two representations are most alike, they look for and make sense of the structure of the number line and deepen their understanding of the relationship between addition and subtraction (MP3, MP7).

• “How do you see each number in the diagram?”
• “How does your equation match the arrow in the diagram? Why does your equation start with ___? Where is that number in the diagram? Which number in your equation represents the length between ___ and ___?”

• Invite previously identified students to share their equations for each number line.
• Consider asking:
  • “Do you agree or disagree? Explain.”
  • “Can anyone explain in another way why _____’s equation matches the number line?”
• Invite previously identified students to share the number lines they feel are most alike.
• If time allows, ask, “In what other ways are the number lines alike? How are they different?”