Family Support Materials. Unit: 2.4 Addition and Subtraction on the Number Line (Grade 2). 2.4 Addition and Subtraction on the Number Line Unit Goals Students learn about the structure of a number line and use it to represent numbers within 100. They also relate addition and subtraction to length and represent the operations on the number line. Section A Goals Represent whole numbers within 100 as lengths from 0 on a number line. Understand the structure of the number line. Section B Goals Represent sums and differences on a number line. Read More Lessons Resources Assessments Practice Glossary Lessons Section A: The Structure of the Number Line 1 Whole Numbers on the Number Line 2