Lesson 14
Which Equation Matches?
Warmup: Which One Doesn’t Belong: Equations (10 minutes)
Narrative
Launch
 Groups of 2
 Display the image.
 “Pick one that doesn’t belong. Be ready to share why it doesn’t belong.”
 1 minute: quiet think time
Activity
 “Discuss your thinking with your partner.”
 2–3 minutes: partner discussion
 Share and record responses.
Student Facing
Which one doesn’t belong?
 \(10 = 6 + 4\)
 \(16  5 = 11\)
 \(11 = 6 + 4 + 1\)
 \(3 + \boxed{\phantom{8}} = 11\)
Student Response
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Activity Synthesis
 “Let’s find at least one reason why each one doesn’t belong.”
Activity 1: Sort Story Problems (15 minutes)
Narrative
The purpose of this activity is to sort story problems with unknowns in all positions. Students sort the story problems by whether they are addition or subtraction problems. Some stories include actions that would be represented by one operation, but may be solved using the opposite operation. Students may sort these problems into either category as long they can explain how they sort.
For example, consider this Take From, Start Unknown story problem:
Clare has some stickers.
She gives 9 of them to her friends.
She has 5 stickers left.
How many stickers did Clare have to start with?
In the last lesson, students related this type of problem to a subtraction equation (\( ?  9 = 5\)). This equation shows a way to use equations to represent the actions in the story. However, students may also think of an equation that shows how they would solve the problem (\(5 + 9 = ?\)). This is discussed in the activity synthesis to prepare students to identify more than one equation to match these story problems in the next activity.
Supports accessibility for: Organization, Attention
Required Materials
Materials to Gather
Materials to Copy
 Story Problem Cards, Unknowns in All Positions
Required Preparation
 Create a set of cards from the blackline master for each group of 2.
Launch
 Groups of 2
 Give each group a set of cards and access to connecting cubes in towers of 10 and singles.
 “We have been solving stories about people doing different arts and crafts. Making collages is another popular craft.”
 Display the word “collage” for all to see and invite students to share what they know about making a collage.
 If needed ask, “What materials can you use to make a collage?” (stickers, pictures, stamps, markers, glitter, glue)
Activity
 “Today we are going to look at lots of stories about students who made collages. Sort the story problems by whether they are addition or subtraction. Be ready to explain how you know so that others can understand.”
 10 minutes: partner work time
 Monitor for two groups who put the same story problem in different categories.
Student Response
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Activity Synthesis
 Display the problems that students sorted into different groups (for example, A1, A5 or A6).
 “How is this an addition story problem? How is this a subtraction story problem?” (To solve card A1, I can think about how many pictures to add to 8 to get to 11, or I can think \(11  8\) to find how many pictures there are.)
 Repeat with other problems as time permits.
Activity 2: Stories and Equations (20 minutes)
Narrative
The purpose of this activity is to match equations to the story problems from the previous activity. Each story has several equations listed, two of which match the story. Students are encouraged to find both equations; however, it is more important that students can explain how an equation represents what is happening in the story, or how it is used to solve the story. In the launch, students make sense of a familiar diagram to encourage them to use objects or drawings to represent the story if it will help them find the matching equations.
In order to match stories with equations, students reason abstractly and quantitatively (MP2) as they interpret both the numbers and the operations in the equations in terms of a context.
Advances: Speaking, Conversing
Required Materials
Materials to Gather
Launch
 Groups of 2
 Give students access to connecting cubes in towers of 10 and singles.
 Display the diagram and read the first story problem. Do not display the equations.
 “How does the diagram represent the story problem?” (The eight white cubes show the pictures of people. The three blue cubes were added to get to a total of 11. So the three blue cubes show the pictures of animals.)
 1 minute: quiet think time
 1 minute: partner discussion
 “Which equations match the story?”
 Display the equations.
 30 seconds: quiet think time
 1 minute: partner discussion
 Monitor for students who chose the second and third equations.
 Invite students to share.
 If needed: “How does the diagram match the equation?”
 “There is an addition and subtraction equation that can match this problem.”
Activity
 Read the task statement.
 10 minutes: partner work time
Student Facing
For each problem, circle the 2 equations that match the story.
You can use objects or drawings to represent the problem, if it helps you.

Jada uses 8 pictures of people.
She also uses some pictures of animals.
Altogether she uses 11 pictures.
How many pictures of animals does she use? \(8 + 11 = {?}\)
 \(8 + {?} = 11\)
 \(11  8 = {?}\)

Kiran has 19 pictures.
He gives some to his sister.
Now, he has 11 pictures left.
How many pictures did Kiran give to his sister? \(11 + 19 = {?}\)
 \(19  {?} = 11\)
 \(19  11 = {?}\)

Han’s collage has 16 stamps.
Lin’s collage has 10 fewer stamps.
How many stamps does Lin’s collage have? \(10 + 16 = {?}\)
 \(10 + {?} = 16\)
 \(16  10 = {?}\)

Elena uses 9 more stickers than Andre.
Andre uses 5 stickers.
How many stickers does Elena use? \(9 + 5 = {?}\)
 \(5 + 9 = {?}\)
 \(9  5 = {?}\)

Noah has 6 stamps.
Tyler has 16 stamps.
How many fewer stamps does Noah have than Tyler? \(6 + {?} = 16\)
 \(16  6 = {?}\)
 \({?}  6 = 16\)

Clare has some stickers.
She gives 9 of them to her friends.
She has 5 stickers left.
How many stickers did Clare have to start with? \(5 + 9 = {?}\)
 \(9  5 = {?}\)
 \({?}  9 = 5\)
If you have time: Choose a story problem to solve.
Show your thinking using drawings, numbers, or words.
Student Response
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Activity Synthesis
 Display the problem about Noah and Tyler and a tower of 6 cubes and a tower of 16 cubes.
 “Use the cubes to explain how we can use addition to solve this problem.”

Repeat for subtraction.
Lesson Synthesis
Lesson Synthesis
Display story problem A2:
Kiran has 19 pictures.
He gives some to his sister.
Now he has 11 pictures left.
How many pictures did Kiran give to his sister?
 \(11 + ? = 19\)
 \(19  ? = 11\)
 \(19  11 = ?\)
“Which equation best matches the actions in this story? Why?” (\(19  \underline{\hspace{1 cm}} = 11\) because in the story Kiran starts with 19 pictures, he gives some away, and the story tells us he has 11 left.)
“Which equation matches how you would solve this problem? Why?” (I would use \(19  11 = \underline{\hspace{1 cm}}\) because I if I take away the pictures he has left, I will know how many he gave to his sister. I would use \(11 + \underline{\hspace{1 cm}} = 19\) because I would rather add than subtract. I can add to the 11 pictures he had left until I get to 19 and that will tell me how many he gave to his sister.)
Cooldown: Find the Match (5 minutes)
CoolDown
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