Lesson 26

The purpose of this lesson is for students to solve addition and subtraction story problems with the unknowns in all positions.

In previous lessons, students solved Add To, Start or Change Unknown and Take Away, Change or Result Unknown story problems. In this lesson, students apply addition and subtraction methods learned in this unit to solve story problems. In the first activity, students solve two story problems that highlight the relationship between addition and subtraction. In the second activity, students solve more story problems with missing values in all positions. Students do a gallery walk in order to analyze how their classmates solved and compare their representations.

In this lesson students have an opportunity to make sense of problems and persevere in solving them as they solve closely related story problems many of which can be solved with either addition or subtraction (MP1). The focus of the discussion is on how students interpreted the problem and how they used mathematics to model a solution (MP4).

As you finish up this unit, reflect on the norms and activities that have supported each student in learning math. How have you seen each student grow as a young mathematician throughout this work? How have you seen yourself grow as a teacher? What will you continue to do and what will you improve upon in Unit 4?