# Lesson 4

Result or Change Unknown

## Warm-up: True or False: Equations with 10 (10 minutes)

### Narrative

The purpose of this True or False is to give students an opportunity to deepen their understanding of the equal sign. This is the first time that students will do this instructional routine. Because equations are new to students, the teacher should read aloud each equation. When students are more familiar with equations, they will read the equations themselves when they do this routine. In the activity synthesis, students are asked to reword another student's thinking and justify the answer in a different way (MP3).

### Launch

• 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

### Activity

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

### Student Facing

Is each statement true or false?
Be prepared to explain your reasoning.

• $$10 = 10$$
• $$4 + 6 = 10$$
• $$2 + 7 = 10$$

### Activity Synthesis

•  “Who can restate _____'s reasoning in a different way?”
• “Does anyone want to add on to _____’s reasoning?”

## Activity 1: Compare the Problems (15 minutes)

### Narrative

The purpose of this activity is for students to represent and solve an Add To, Result Unknown or Change Unknown story problem. Students then compare each problem, including how the problem is written and how the problem is solved. Each group creates a representation and writes an equation to match one of the problems. Groups then pair up to share their work. Students attend to precision and use clear and precise language to explain how they solved and represented the problem (MP6). The activity synthesis draws out differences in the story problems as well as differences in how they are solved.

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give students tools for creating a visual display and access to 10-frames and connecting cubes or two-color counters.
• "Today we are going to solve more story problems. The problems today are about different kinds of books. What kinds of books do you like to read?"
•  30 seconds: quiet think time
• 2 minutes: partner discussion
•  Share responses.
•  "Let's see what kinds of books the people in our stories like to read."

### Activity

• Assign each group one of the problems.
• “Make a poster that shows your answer to the problem. It must have a drawing and an equation. Be ready to explain how you solved it and how you knew what equation to write.”
• 5 minutes: partner work time
• "Now find another group to work with that solved the other problem. Each group of 2 shares their poster, including how they solved the problem and how they know the equation they wrote matches the story problem.”
• 4 minute: small group discussion

### Student Facing

1. Mai has 5 graphic novels.
She checks out 4 more.
How many graphic novels does she have?
Show your thinking using drawings, numbers, or words.

Equation: ________________________________

2. Mai has 5 graphic novels.
She checks out some more.
Now she has 9 graphic novels.
How many graphic novels did she check out?
Show your thinking using drawings, numbers, or words.

Equation: ________________________________

### Activity Synthesis

• Display both problems and student posters of how each problem was solved.
• “What differences do you see between the two story problems?” (In problem 1, we know how many books Mai checked out, but in problem 2 we don’t. In problem 1 we don’t know how many books she has total, but in problem 2 we do.)
• “How do these differences affect how you solve the problem?” (In problem 1, we just drew 5 books and 4 more books. Then we had to count how many there were altogether. In problem 2, we had to start with 5 books, and draw more until we had 9. Then count how many more we drew.)

## Activity 2: Story Problems about Books (20 minutes)

### Narrative

The purpose of this activity is for students to solve a variety of Add to and Take from Result or Change Unknown story problems. Students solve the story problems any way they choose and write an equation that matches the story and has a box around the answer to the question. During the activity synthesis, students consider the different ways to write equations for a story problem.

MLR8 Discussion Supports. Synthesis: For each method that is shared, invite students to turn to a partner and restate what they heard using precise mathematical language.
Engagement: Develop Effort and Persistence. Chunk this task into more manageable parts. Check in with students to provide feedback and encouragement after each chunk.
Supports accessibility for: Social-Emotional Functioning, Attention

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give students access to 10-frames and connecting cubes or two-color counters.
• "We are going to solve some more story problems about books other kids like to read."

### Activity

• 5 minutes: independent work time
• 5 minutes: partner discussion

### Student Facing

Diego gives her 4 more books to read.
Show your thinking using drawings, numbers, or words.

Equation: ________________________________

2. Noah has 4 books of poetry.
His sister gives him some more books.
Now he has 10 books of poetry.
How many books did his sister give him?
Show your thinking using drawings, numbers, or words.

Equation: ________________________________

3. Tyler has 7 books about spiders.
He gives 3 of his books to Kiran.
How many books does Tyler have left?
Show your thinking using drawings, numbers, or words.

Equation: ________________________________

4. Lin has 5 books about outer space.
Her teacher gives her some more books.
Now she has 10 books about outer space.
How many books did Lin's teacher give her?
Show your thinking using drawings, numbers, or words.

Equation: ________________________________

### Activity Synthesis

• Invite students to share the equation for each problem.
• "Why is the answer in different places in our equations?" (Because in some stories we know the two numbers to add together and then the answer is the total. In other problems we know the starting number and the total and the answer is the other number we added.)

## Lesson Synthesis

### Lesson Synthesis

Display the problem about Lin's books and $$5 + \boxed{\phantom{5}} = 10$$.

“Today we wrote equations to match story problems and discussed differences in the equations. Look at the problem and the equation. What do you notice? What do you wonder?” (I see a blank box. I notice the equation matches the story problem. It starts with 5, then some more are added, and that is the same amount as 10. I wonder if 5 goes in the blank box.)

If needed, ask “How does this story problem connect to the equation $$5 + \boxed{\phantom{5}} = 10$$ ?” ($$5 + \boxed{\phantom{5}}$$ represents Lin’s 5 books and the number of books her teacher gives her. The 10 represents how many books she has about outer space now. The blank box is where the 5 goes since that is the answer to the question.)

## Student Section Summary

### Student Facing

We solved story problems and represented them with objects, drawings, words, and equations.

• We solved story problems with addition.

Diego gives her 4 more books to read.

• We solved story problems with subtraction.

Tyler has 7 books about spiders.
He gives 3 to Kiran to read.
How many books does Tyler have left?

• We solved story problems where the change was unknown.

Lin has 5 books.
Her teacher gives her some more books.
Now she has 10 books to read.
How many books did her teacher give her?

• We learned that the equal sign means “the same amount as” and “equals.”