Lesson 6

This warm-up prompts students to carefully analyze and compare equations. In addition to calculating the value of each expression, students also think about the structure of each expression, including both the operations and the numbers (MP7). In the synthesis, students compare an equation with addition and an equation with subtraction to focus student attention on comparing operations and reasoning about the relationship between addition and subtraction. 

• Groups of 2
• Display image.
• “Pick one that doesn’t belong. Be ready to share why it doesn’t belong.”
• 1 minute: quiet think time

• “Discuss your thinking with your partner.”
• 2-3 minutes: partner discussion
• Share and record responses.

• Display equations B and C.
• “How are the equations the same? How are they different?” (They both have the value 11. The first equation uses subtraction while the second one uses addition. The 11 is on the right hand side in the first equation and on the left hand side in the second equation. In the second equation 11 is written using three numbers and there are only two in the first equation.)

The purpose of this activity is for students to practice solving Compare, Difference Unknown story problems (MP2). In the synthesis, students revisit a representation of a Compare problem that was introduced in a previous unit. This representation lays the foundation for working with tape diagrams in grade 2. 

The teacher may want to incorporate movement into this activity by writing each problem on a piece of chart paper and placing each one in a different location around the classroom. Students can solve the problem at one location, discuss the problem with their partner, then move on to a new problem at a new location. 

• Groups of 2
• Give each group access to connecting cubes in towers of 10 and singles.
• “Today we are going to solve some problems about a school carnival. What are some things you know about carnivals?” (There are rides. You can play games. There is lots of food.)

• Read the task statement.
• 8 minutes: independent work time
• 4 minutes: partner work time
• For the problem about prizes, monitor for students who:
  • use cubes or draw pictures to represent both quantities.
  • write equations with a symbol to represent the unknown.
  • write equations to show how they used addition or subtraction to find the difference.

If students add both quantities in the problems, consider asking:

• “What is the problem about? What do you know? What do you need to figure out?”
• “What did you do to solve the problem?”
• “What does your answer mean in the story? Does it make sense?”
• “How could you use the connecting cubes or a drawing to represent the problem?”

• Invite previously identified students to share.
• “How do these representations match the story?”
• If needed, “Where do you see how many fewer stuffed animals there are than toys?”
• If needed, “What equations can we write to represent this problem?”

The purpose of this activity is for students to use given information to ask and answer different questions. Students may ask Put Together or Compare problems using the given information. A representation of the information is also provided. This representation is a precursor to the tape diagrams students will use to represent and solve Compare problems in grade 2.

When students recognize the mathematical features of things in the real world and ask questions that arise from a presented situation, they model with mathematics (MP4).

• Groups of 2
• Give each group access to connecting cubes in towers or 10 and singles.

• Read the task statement.
• 15 minutes: partner work time
• Monitor for students who can explain how the representation helps them answer the question they asked.

• Display the representation in the student book. 
• Invite previously identified students to share their question and how the representation helps them find the answer to the question.