This Problem Set is a part of the Lesson 5, Unit 1, Grade 2. In this lesson, students continue use the "make ten" strategy now using a two-digit addend. For example, to add 39 + 4, students decompose 4 as 1 and 3 in order to complete a unit of ten (39 + 1) and then add, or compose, the ten with the remaining ones (40 + 3).
