The purpose of this activity is for students to sort addition expressions, based on their perceived difficulty. They find the values of expressions they feel are less challenging and expressions they feel are more challenging. Then they compare the methods they use for the expressions they solve with their peers. When sharing, students have opportunities to ask questions about the methods and representations their peers use and suggest methods or representations for expressions that their peers may feel are difficult to solve (MP3).

When students sort the expressions, they look for place value structure to determine how they would find the sums (MP7).

• “How could using what you know about sums of 10 help you sort these expressions?”
• “How could you arrange your expressions in order of ‘least challenging’ to ‘most challenging’?”

• Invite a previously identified student to share how they found the value they felt was less challenging.
• “What questions do you have for _____ about their method?”

• Display question starters:
  • “Why did you . . . ?”
  • “Can you say more about . . . ?”
  • “Did you think about trying . . . ?”
• 1 minute: quiet think time
• Invite 2–3 students to ask questions.
• Repeat with a previously identified student to share a value they felt was more challenging to find.
• If time, continue to select students to share strategies for expressions that they felt were less or more challenging.

• Invite previously identified students to share their work.
• “How did _____ find the unknown number?” (They started by adding the 85 to the 615 to get 700. Then they knew they needed 3 hundreds more to get to 1,000.)
• Share responses and record with equations and on an open number line.