This Problem Set is a part of the Lesson 1, Unit 2, Grade 1. In this lesson, students solve word problems with three addends as a way for them to begin to explore the "make ten" strategy in a meaningful context. With problems that always include at least two numbers that yield 10 when added together, this lesson encourages students to use the associative and commutative properties as they set up and read equations in various ways. For example, students can solve the story problem "We had 1 upper-grade buddy come visit with 9 more buddies following him.