# Lesson 14

Expressions and Story Problems

## Warm-up: Choral Count: Count On (10 minutes)

### Narrative

The purpose of this warm-up is to count on from a given number. As students count, point to the numbers posted so that students can follow along. To support students as they learn to count on, consider asking “What number comes after 3?” or providing a running start by counting “1, 2, 3…” and having students continue the count.

### Launch

• “Let’s count to 10.”
• Count to 10.

### Activity

• “Now start at the number 3 and count to 10.”
• Count on from 3 to 10.
• Repeat 3–4 times starting with other numbers within 10.

### Activity Synthesis

• “We can start counting at numbers other than 1. When we count on, we think about what number comes next when we count.”

## Activity 1: Expression for a Story Problem (10 minutes)

### Narrative

The purpose of this activity is for students to explain how a subtraction expression represents a story problem (MP2). Students connect the expression to the story problem and then solve the story problem. Students will be introduced to equations in a later unit.

MLR8 Discussion Supports. Invite students to use connecting cubes or counters with verbal descriptions to explain what happened in the story problem.

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• “Tell your partner what happened in the story.”
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Monitor for students who accurately retell the story. Choose at least one student to share with the class.
• Write the expression $$10 - 6$$.
• “How does this expression show what happens in the story problem?”
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Share responses.

### Activity

• “Show your thinking using drawings, numbers, words, or objects.”
• 2 minutes: independent work time
• 2 minutes: partner discussion

### Student Facing

There were 10 people riding bikes in the park.

Then 6 of the people stopped riding to have lunch.

How many people are riding bikes now?

### Activity Synthesis

• Write “$$10 - 6$$.”
• “What does the 10 represent in the story problem? What does the 6 represent?”
• “10 take away 6 is 4. We can write that as $$10 - 6$$ is 4.”

## Activity 2: Which Expression? (10 minutes)

### Narrative

The purpose of this activity is for students to choose expressions that represent story problems (MP2).

Representation: Develop Language and Symbols. Synthesis: Students may benefit from comparing the two problems and identifying what is different about what happened in the story and the expression that represents the story. Make connections between Lin putting more rocks in her jar and the addition symbol in the expression and the kids that left to go jump rope and the subtraction symbol in the expression.
Supports accessibility for: Visual-Spatial Processing, Conceptual Processing

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• “Which expression shows what happened in the story problem? Tell your partner how you know.”

### Activity

• 30 seconds: quiet think time
• 2 minutes: partner discussion
• Share responses.
• Repeat the steps with the second story problem and expressions.

### Student Facing

1. There were 2 rocks in Lin’s jar.
At the park, Lin put 4 more rocks into her jar.
How many rocks are in Lin’s jar now?

$$3 + 3$$

$$6 - 2$$

$$2 + 4$$

2. There were 8 kids playing hopscotch.
3 of the kids left to go jump rope.
How many kids are playing hopscotch now?

$$8 + 3$$

$$3 - 3$$

$$8 - 3$$

### Student Response

If students match the second story problem with an expression other than $$8 - 3$$, consider asking:

• “Can you tell me what is happening in the story problem?”
• “Is something being added or taken away in the story problem? How can that help you figure out which expression matches?”

### Activity Synthesis

• Display $$8 + 3$$ and $$8 - 3$$. If needed, reread the second story problem.
• “Which expression did you choose? How did you know which expression to choose?” ($$8 - 3$$. Some of the kids left, so I chose the one with the minus sign.)
• Display $$8 - 3$$.
• “Use this expression to tell your partner what happened in the story.”

## Activity 3: Centers: Choice Time (25 minutes)

### Narrative

The purpose of this activity is for students to choose from activities that offer practice writing numbers and telling and solving story problems. Students choose from any stage of previously introduced centers.
• Number Race
• Math Stories
Students will choose from these centers throughout the section. Keep materials from these centers organized to use each day.

### Required Materials

Materials to Gather

### Required Preparation

• Gather materials from:
• Number Race, Stage 1
• Math Stories, Stages 1 and 2

### Launch

• “Today we 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 first.”
• 30 seconds: quiet think time

### Activity

• Invite students to work at the center of their choice.
• 10 minutes: center work time
• “Choose what you would like to do next.”
• 10 minutes: center work time

Choose a center.

Number Race

Math Stories

### Activity Synthesis

• “What was your favorite story problem that your partner told you? Why was it your favorite?”

## Lesson Synthesis

### Lesson Synthesis

There were 10 people riding bikes in the park.
Then 6 of the people stopped riding to have lunch.
How many people are riding bikes now?

Display $$10 + 6$$.

“Han says that $$10 + 6$$ matches this story problem because there are 10 people first and then there are 6 people. What do you think?” (It doesn't match. 6 people stopped riding bikes, so you need to use $$10 - 6$$.)