Lesson 14

The purpose of this True or False is to continue to develop and deepen student understanding of the equal sign. These understandings will be helpful when students work with equations with expressions on both sides of the equal sign in a later unit.
This is the second time students will do this instructional routine. The teacher should read aloud each equation. When students are more familiar with equations, they do not need to be read by the teacher.

• Display one statement.
• “Give me a signal when you know whether the statement is true and can explain how you know.”
• 1 minute: quiet think time

• Share and record answers and strategy.
• Repeat with each equation.

• “How is 10 the same amount as \(7 + 3\)?” (When I add 7 and 3, the total is 10.)
• “If \(7 + 3 = 10\), and \(10 = 7 + 3\), would \(10 = 3 + 7\)?” (Yes, because 7 + 3 is the same amount as 10, and 10 is the same amount as \(3 + 7\).) 

The purpose of this activity is for students to explore the relationship between addition and subtraction through a Compare, Difference Unknown story problems. They analyze two equations, one addition and one subtraction, that match the same problem and discuss the relationship between the two equations and the story problem. Students should notice that both equations can be used to describe how they solve the problem. This also helps them relate addition and subtraction and see that often either operation can be used to solve a problem (MP7).

• Groups of 2
• Give students access to connecting cubes or two-color counters.
• Display the image in the student book.
• “Tell a story about this picture.”
• 1 minute: quiet think time
• 2 minutes: partner discussion
• Share responses.

• Read the task statement.
• 5 minutes: partner work time
• Encourage students to use the representation to make sense of both equations.
• Monitor for a group who uses the representation to explain the addition equation and one who explains the subtraction equation.

If students find the difference using only one operation, consider asking:

• "Can you explain how you found the difference between the number of glue sticks and scissors?"
• "Where in your drawing (objects) do you see the difference? How could you find that part of the representation by adding (subtracting)?"

• “What are we trying to find out in this story problem?” (How many fewer scissors there are than glue sticks. The difference between the number of scissors and glue sticks.)
• Invite previously identified groups to share. 
• “What is the same? What is different?” (3, 5, and 8 are in each equation. The numbers represent the same things in both. The 5 is boxed in both. One uses addition and the other uses subtraction. The boxed number is in a different place.)

The purpose of this activity is for students to identify addition and subtraction equations that match Compare, Difference Unknown story problems. Students may not initially choose more than one equation for each problem, so this is the emphasis of the activity synthesis. Students continue to build their language of Compare problems and solidify the relationship between addition and subtraction.

• Groups of 2
• Give students access to connecting cubes or two-color counters.

• Read the task statement.
• 3 minutes: independent work time
• 2 minutes: partner discussion
• Monitor for a student who can show and explain how they chose which equation matches.

• “How did you know which equation matched the problem about backpacks?" (I made a tower of 3 cubes to show the purple backpacks, and a tower of 7 cubes to show the black backpacks. Then I broke off the difference, which is 4. This matches 7 - __ = 3 because the 4 shows the difference.)
• “Are there any other equations that represent this problem?” (Yes, 3 + ___ = 7 also matches. I started with 3 cubes, and added cubes until I got to 7. The amount I added was 4.)
• "There were two equations that match this problem. Check the other problems to see if there are any other equations that match."

The purpose of this activity is for students to choose from activities that offer practice telling and solving story problems and adding and subtracting within 10. Students choose from any stage of previously introduced centers.

• Capture Squares
• Math Stories
• Shake and Spill

• Gather materials from previous centers:
  • Capture Squares, Stage 1
  • Math Stories, Stage 4
  • Shake and Spill, Stages 3 and 4

• Groups of 2
• “Now you are going to choose from centers we have already learned.”
• Display the center choices in the student book.
• “Think about what you would like to do.”
• 30 seconds: quiet think time

• Invite students to work at the center of their choice.
• 10 minutes: center work time

• “Tell your partner one thing they did that helped you during center time today.”