Lesson 16

The purpose of this Number Talk is to activate students’ previous experiences with addition methods involving composing a ten. In previous lessons, students used their knowledge of making a ten to find sums within 20 and used methods based on place value to compose a ten when adding within 100. This string is designed to encourage these methods. 

• 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.

• "How do you think the third expression could help with finding the value of the fourth one?" (In the ones place there was a 6 and 7, so I knew that \(6 + 4 = 10\) and there were 3 left over. In the fourth expression the ones were switched, but it was still 10 with 3 left over.)

The purpose of this activity is for students to create a line plot from data presented in a table. The table includes data with longer lengths and a greater difference between the shortest and longest lengths than the data used in previous lessons. Students make decisions about how to label the number line using what they have learned about the structure of line plots and how to represent and label measurement data. The synthesis discussion focuses on sharing and comparing the strategies students used to create their line plots, focusing on how they chose which numbers to use on their line plots (MP3).

• Groups of 2
• Give each student the Line Plot Template.
• Display the table showing plant heights.
• “Second grade students were growing plants in science class. They each measured the height of their plants. Height tells us the length of the plant from the soil to the top of the stem.”
• “Here is how they represented their data.”
• 30 seconds: quiet think time

• “Your job is to create a line plot to represent this data. Think about how you want to label the tick marks with numbers. Be sure to include a title, label your units of measure, and think about how you are drawing your Xs so others can easily read your data.”
• 8 minutes: independent work time
• “Compare your line plot with your partner’s.”
• 2 minutes: partner discussion
• Monitor for students with clear and accurate line plots.

• Invite 2–3 students to display their line plots.
• Consider asking each student:
  • “How did you decide which numbers to start and end your line plot with?” (I looked at the table to find the shortest and longest lengths.)
• “How are these line plots the same? How are they different?”
• “What can you say about the height of their plants by looking at the line plot?” (There are 3 Xs over 33, so those plants all measured 33 cm. Only 1 plant was 27 cm.)
• “How many students had a plant that measured more than 30 cm?” (4 because 3 had 33 and 1 had 35).

The purpose of this activity is to interpret measurement data represented by line plots. Students use the line plots they created in the previous activity and another line plot about plant heights to answer questions. In the activity synthesis, students share how they found the difference between two lengths using the line plot and discuss how the structure of the line plot helps to show differences (MP7).

• Groups of 2

• “Now you are going to use the line plots you have created to answer questions about the measurement data.”
• “You will also answer a few questions based on a line plot created by Han.”
• 8 minutes: independent work time
• Monitor for students who notice they can count the length units on the line plot to find the difference between the tallest and shortest plant.
• “Check your answers with your partner and share what you learned about Han's line plot.”
• 3 minutes: partner discussion
• Monitor for a variety of student statements about Han's line plot to share in the lesson synthesis.

• Invite 1–2 students to share how they found the difference between the height of the tallest and shortest plants on their line plot.
• “How does the line plot help you see differences in the measurements that are collected?” (Each tick mark is the same length apart. You can count the distance between each. You can see if there’s a big or small difference between the measurements by how they are spread out.)