The purpose of this activity is for students to interpret a Compare problem with the smaller value unknown and connect the problem to a tape diagram. The Launch of the activity is an opportunity for students to share their experiences and ask questions about a beach to ensure each student has access into the context. If it is helpful, display a few images of beaches from different areas around the world. The story problem is introduced without numbers in order to allow students to consider the relationship between quantities. Students consider who has more or less, which supports their interpretation of the tape diagram. If needed to help students connect the tape diagram to the subtraction equation, show students that if you look at Diego’s rectangle and cover up the portion below that part that shows 20, it will be the same as Lin’s rectangle.

At the beginning of this activity, make sure students do not have their student books open yet.

• Invite previously identified student(s) to explain how they labeled the tape diagram.
• Consider asking:
  • “¿Qué parte representa las conchas marinas de Diego? ¿Cómo lo saben?” // “Which part represents Diego’s shells? How do you know?”
  • “¿Qué parte representa las conchas marinas de Lin? ¿Cómo lo saben?” // “Which part represents Lin’s shells? How do you know?”
  • “¿Qué parte muestra la diferencia entre la cantidad de conchas marinas que tiene cada estudiante?” // “Which part shows the difference between the amount of shells each student has?”
  • “¿Alguien podría explicar cómo _____ decidió marcar el diagrama?” // “Could someone explain how _____ decided to label the diagram?”
• Invite previously identified student(s) to share the equation they used to represent the story problem.
• “¿Cómo usaron el diagrama para escribir su ecuación?” // “How did you use the diagram to write your equation?” (The diagram helped me see that I could start with 55 and take away 20 to find Lin’s shells. The diagram helped me see that Lin’s shells and 20 more would be the same as 55.)
• Consider having student(s) describe what the numbers and symbols in the equation represent, as they did for the diagram.

The purpose of this activity is for students to connect Compare problems, tape diagrams, and equations with unknowns in all positions. Support students with interpreting “more” or “fewer” in the context of the story problem by encouraging them to explain which quantity should be the bigger quantity and which should be the smaller quantity. Ask them to describe what they look for in a diagram or equation to make sure it matches a story problem. When students analyze and connect the quantities and structures in the story problems, diagrams, and equations, they think abstractly and quantitatively (MP2) and make use of structure (MP7).

If students are not yet reading independently, consider reading one story problem at a time and giving students time to independently find their matches. It is recommended to read the story problems in order beginning with story problem A if facilitated in this way.

• Invite 2–3 student groups to share how they decided which cards go together. Consider selecting groups to share their matches for story problems A, B, and C.
• Consider asking:
  • “¿Cómo saben que el diagrama corresponde al problema-historia?” // “How do you know the diagram matches the story problem?”
  • “¿Cómo corresponde su ecuación al problema-historia?” // “How does your equation match the story problem?”
  • “¿Hay otra ecuación que puede corresponder a su problema-historia? ¿Cómo lo saben?” // “Is there another equation that could match your story problem? How do you know?”