# Lesson 9

Compare Story Problems

## Warm-up: Number Talk: Addition and Subtraction Expressions (10 minutes)

### Narrative

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.

### Launch

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

### Activity

• Keep expressions and work displayed.
• Repeat with each expression.

### Student Facing

Find the value of each expression mentally.

• $$4 + 6$$
• $$6 + 4$$
• $$10 - 6$$
• $$10 - 4$$

### Activity Synthesis

• “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?”

## Activity 1: Solve and Represent Story Problems (20 minutes)

### Narrative

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.

MLR8 Discussion Supports. Some students may benefit from the opportunity to act out the scenario. Listen for and clarify any questions about the context of each problem.

### Required Materials

Materials to Gather

### Launch

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

### Activity

• "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

### Student Facing

1. Han has 5 lizards.
He has 3 snakes.
How many pets does he have?

Show your thinking using drawings, numbers, or words.

Equation: ____________________________

2. Han has 8 pets.
5 of his pets are lizards.
The rest of his pets are snakes.
How many snakes does Han have?
Show your thinking using drawings, numbers, or words.

Equation: ____________________________

3. Han has an aquarium that can hold 8 pets.
He has lizards and snakes.
Show different ways Han could fill his aquarium.
Show your thinking using drawings, numbers, or words.

Equation: ____________________________

### Activity Synthesis

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

## Activity 2: Gallery Walk: Compare the Story Problems (20 minutes)

### Narrative

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.

Action and Expression: Internalize Executive Functions. Check for understanding by inviting students to rephrase directions in their own words. Keep a display of directions visible throughout the activity.
Supports accessibility for: Memory, Organization

### Required Preparation

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

• Groups of 6

### Activity

• "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.

### Student Facing

1. What is the same about the story problems and representations?

2. What is different about the story problems and representations?

3. Explain how the equation matches the story problem.

### Activity Synthesis

• “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?”

## Lesson Synthesis

### Lesson Synthesis

Display the problem, 'Han has 8 pets. 5 of his pets are lizards. Some of his pets are snakes. How many snakes does Han have?'

“Today we solved story problems and wrote equations to match the stories. We said that the equation $$5 + \boxed{3} = 8$$ matches this problem.”

Display $$8 - 5 = \boxed{3}$$.

“Could this equation represent the problem? Why or why not?” (Yes. If I think about 8 pets, I can subtract the number of lizards to tell me how many snakes I have.)

If needed, draw 8 circles and label the first 5 as lizards.

“We will discuss more about how we can represent some problems as addition or subtraction in the next part of our unit.”

## Student Section Summary

### Student Facing

In this section, we solved story problems.

• We solved story problems where the total was unknown.

Kiran has some fish in his fish tank.
He has 4 red fish and 5 blue fish.
How many fish does he have in all?

$$4 + 5 = \boxed{9}$$

• We solved story problems where both parts were unknown.

Tyler is playing Shake and Spill.
He is playing with 10 counters.

Show different combinations of red and yellow counters that Tyler could spill.

$$\boxed{4} + \boxed{6} = 10$$

$$\boxed{6} + \boxed{4} = 10$$

$$\boxed{5} + \boxed{5} = 10$$

$$\boxed{7} + \boxed{3} = 10$$

• We solved problems where the second part was unknown.

6 counters are outside the cup.
Some of the counters are under the cup.
There are 10 counters total.
How many counters are under the cup?

I can count on from 6 to 10.

$$6 + \boxed{4} = 10$$

• We learned that the total can come before or after the equal sign.

$$10 = 4 + 6$$ is the same as $$4 + 6 = 10$$

• We learned that numbers can be added in any order.

$$4 + 6 = 10$$ is the same as $$6 + 4 = 10$$