The purpose of this activity is for students to add and subtract within 1,000. Students begin the activity by analyzing different expressions without adding or subtracting to determine which values they think would be the least and most challenging to find. In the Synthesis, students share different reasons why sums and differences were chosen to be “least” and “most challenging” and different methods for finding the values of the expressions.

Although students may have many different reasons for why they think finding the values of some expressions is more or less challenging, the Synthesis focuses on reasons based on composing or decomposing units. Discussing whether students will compose or decompose units will support students in fluently finding sums and differences within 100 in the next activity.

This activity uses MLR8 Discussion Supports. Advances: speaking.

• Poll the class. For each expression, ask students to “Show one finger if the expression was not challenging, two fingers if it was a little challenging, or three fingers if it was the most challenging to find.”
• Consider displaying:
  • A, D, E, F, H, J
• Stop for any expressions where there is a mix of ratings.
• Consider asking:
  • “Why did you feel this expression is more challenging?”
  • “Who can share why this expression was less challenging?”
• When most or all students felt an expression was most challenging, select students to share different methods for finding the value.
• “All the expressions you felt were most challenging can become less challenging with practice and using what you know about place value.”

The purpose of this activity is for students to fluently find sums and differences within 100. Students should be encouraged to use whatever method makes the most sense to them, including mental strategies. In the Synthesis, students reflect on which values were least and most challenging to find.

• Share 1–2 expressions that students felt were least challenging.
• Invite previously identified students to share methods they used for finding the value of the sums or differences mentally.
• Share 1–2 expressions that students felt were most challenging.
• Invite previously identified students to share different methods for finding the values.