The purpose of this activity is for students to make sense of and solve Put Together/Take Apart, Addend Unknown story problems (MP2). In the Activity Synthesis, students discuss different methods used to solve these problems, including using addition and subtraction.

The teacher may want to incorporate movement into this activity by writing each problem on a piece of chart paper and placing each one in a different location around the classroom. Students can solve the problem at one location, discuss the problem with their partner, then move on to a new problem at a new location.

• “What is the story problem about? What do you know? What do you need to figure out?”
• “What does your answer mean in the story? Does it make sense?”

• Display and
• “How do both of these equations help you find the number of shooting stars Tyler sees?”
• Invite previously identified students to share. As needed, ask students to connect the numbers they use to the story problem.
• “How are these methods the same? How are they different?” (They both find the same number of dim stars. Both show that there’s some bright stars, some dim stars, and a total number. One way uses addition to count on from the number of bright stars. One way uses subtraction to take away the number of bright stars from the total.)

The purpose of this activity is for students to identify different equations that can be used to represent the same problem. Students explain why each equation does or does not represent the story. This helps students understand that Put Together/Take Apart story problems can be represented and solved with either addition or subtraction when an addend is unknown (MP2).

• For each problem:
  • Invite students to share how each equation they chose represents the problem. 
  • Invite students to share why one of the equations does not represent the problem.