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. This sorting task gives students opportunities to analyze story problems closely and make connections (MP2, MP7). 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 as 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 (). This equation represents the action in the story. However, students may also think of an equation that shows how they would solve the problem (). This concept is discussed in the Activity Synthesis to prepare students to identify more than one equation to match these story problems in the next activity.

• Display the problems that students sorted into different groups, such as Cards A, D or F.
• “¿Por qué este problema-historia se puede ver como un problema de suma? ¿Por qué se puede ver como un problema-historia de resta?” // “How is this an addition story problem? How is this a subtraction story problem?” (To solve Card A’s problem, I can think about how many pictures to add to 8 to get to 11, or I can think to find how many animal pictures Jada uses.)
• Repeat with other problems as time permits.

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.

MLR8 Discussion Supports Display the following sentence frames to support partner discussion: “Pienso que las ecuaciones _____ y _____ corresponden a la historia porque . . .” // “I think the equations _____ and _____ match the story problem because…,” “Estoy de acuerdo porque . . .” // “I agree because…,” and “Estoy en desacuerdo porque . . .” // “I disagree because…”
Advances: Speaking, Conversing

• Display the problem about Noah and Tyler and a tower of 6 cubes and a tower of 16 cubes.
• “Usen los cubos para explicar cómo podemos usar la suma para resolver este problema” // “Use the cubes to explain how we can use addition to solve this problem.”

• Repeat for subtraction.