This Problem Set is a part of the Lesson 24, Unit 1, Grade 1. In this lesson, students build a "ladder" of related facts, and explain how one fact relates to the next. For example, 2 + 1 might lead to 2 + 2 (one more), which might lead to 3 + 3 (the next double), and so on. This helps students build fluency with addition within 10, and reinforces all of the relationships learned in the past several lessons.
