Lesson 9

The purpose of this Number Talk is to elicit strategies and understandings students have for addition and subtraction. These understandings help students develop fluency and will be helpful later in this lesson when students add and subtract to find unknowns in different positions.

• 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.

• “Who can restate _____’s reasoning in a different way?”
• “Did anyone have the same strategy but would explain it differently?”
• “How are all the expressions related?”

The purpose of this activity is for students to solve a variety of Put Together/Take Apart story problems with the unknown in different places. Two of the problems have the same addends and total, with the unknown in different places. The third problem has both addends unknown. Students who are assigned this problem should be encouraged to find multiple combinations for this context. Students may solve in any way that makes sense to them and write equations to match the problem. They write an equation and put a box around the number that represents the answer to the question. After drafting their answer in their books, groups create a poster that includes a labeled drawing and an equation for one of the problems.

Posters will be displayed for a gallery walk in the next activity.

• Groups of 2
• Give each group tools for creating a visual display and access to 10-frames and connecting cubes or two-color counters.

• "You are going to solve different types of story problems that we have been working on. After you solve the problems, you will work with a partner to create a poster representing how you solved one of the problems."
• 6 minutes: independent work time
• Assign each group one of the problems to represent on their poster.
• "On your chart paper, include a labeled drawing that shows how you solved the problem. Also include an equation."
• 8 minutes: partner work time

• Check over your poster to make sure that you have included:
  • a labeled drawing
  • at least 1 equation

The purpose of this activity is for students to interpret representations of Put Together/Take Apart problems with unknowns in different positions. Students explain how each equation matches the story problem it represents (MP2). Students consider an equation that can match two different story problems, but the answer to the question is in a different place. 

Students work in groups of 6 with pairs who worked on different problems. 

This activity uses MLR2 Collect and Display. Advances: conversing, reading, writing. 

• Each group will need the visual displays they created in the previous activity.

• Groups of 6

• "You and your partner will work with two other groups to look at three different posters and talk about how the problems and representations are the same and how they are different. Discuss how each equation matches a story problem and where in the equation you see the answer to the question.”
• 10 minutes: small group discussion

MLR2 Collect and Display

• Circulate, listen for, and collect the language students use to explain how the story problems and equations are the same and different. Listen for: total, equation, not known. 
• Record students’ words and phrases on a visual display and update it throughout the lesson. 

• “What did you notice about how the story problems and equations were the same and different?” (In this one, we had to find how many snakes Han had, but in this one we had to find how many pets he had. The first equation had the 3 in a box to show that he had 3, and in this one the answer was 8, so that is in a box.)
• “Are there any other words or phrases that are important to include on our display?”