Lesson objective: Add by using a number line to count on.

This lesson helps to build fluency with whole number addition and subtraction. A number line is used because this tool supports the strategy of counting on. This work helps students develop their understanding of operations because students are practicing different strategies to become more fluent in adding and subtracting numbers.

Students engage in Mathematical Practice 7 (Look for and make use of structure) as they count on using a number line. Students will learn how to efficiently use a number line by starting at the largest addend and counting on the distance equal to the smaller addend. They will also practice using addition to solve subtraction problems.

**Key vocabulary:**

- number line
- difference
- subtraction
- addition
- strategy