Lesson 17

This Number Talk encourages students to use what they know about place value and decomposing numbers to mentally find the value of each difference. The strategies elicited here will be helpful later in the lesson when students practice subtraction within 100.

• Display one expression.
• “Give me a signal when you have an answer and can explain how you got it.”
• 1 minute: quiet think time

• Record answers and strategy.
• Keep expressions and work displayed.
• Repeat with each expression.

• Consider asking:
  • “Who can restate _____ ’s reasoning in a different way?”
  • “Did anyone have the same strategy but would explain it differently?”
  • “Did anyone approach the problem in a different way?”
  • “Does anyone want to add on to _____’s strategy?”

The purpose of this activity is for students to learn stage 1 of the Creating Line Plots center. In this stage, students measure up to 8 objects to the nearest centimeter or inch. They work with a partner to create a line plot to represent their measurement data. Then, they ask their partner 2 questions that can be answered based on their line plot.

• Gather collections of objects of various lengths. Collections could include pencils, crayons, math tools, or other classroom materials that have varying lengths.

• Groups of 2
• Give each group rulers and a line plot template. 
• “We are going to learn a new center. The Creating Line Plots center.”
• “You can measure up to 8 objects to the nearest centimeter or inch. Then work with your partner to create a line plot to represent your data. After that, you take turns asking your partner 2 questions that can be answered based on your line plot.”

• 15 minutes: partner work time
• Monitor for a variety of questions students ask their partners about their line plots.

• Display a student created line plot.
• “Work with your partner to come up with a question that can be answered based on this line plot.”
• Invite students to ask the class their question and have the class answer based on the line plot. 

The purpose of this activity is for students to choose from activities that focus on addition and subtraction within 100 and estimation and measurement. If students choose the Estimate and Measure center as their first choice, they may choose to represent their measurements in a line plot using the Creating a Line Plots center materials as their second choice.

Students choose from any stage of previously introduced centers.

• Estimate and Measure
• Number Puzzles
• Target Measurements

Gather materials from:

• Estimate and Measure, Stage 2
• Number Puzzles, Stages 2–4
• Target Measurements, Stage 1

• “Now you will choose from centers we have already learned.”
• Display the center choices in the student book.
• “Think about which activity you would like to do first. If you start with Estimate and Measure now, you can use your measurements in the Creating Line Plots center as your second choice.”
• 30 seconds: quiet think time

• Invite students to work at the center of their choice. 
• 8 minutes: center work time
• “Choose what you would like to do next.”
• 8 minutes: center work time

• “What did you like about the activities you worked on today?"