This Problem Set is a part of the Lesson 4, Unit 3, Grade 3. In this lesson, students count by sixes, composing up to and then over the next ten. For example, they might count 6, 12, 18, and then add 18 + 2 + 4 to make 24. (In doing so, they utilize the "make a ten" strategy first introduced in Grades 1. and 2.)