Lesson objective: Solve 2-step story problems that involve addition and/or subtraction using a number line.

This lesson provides an opportunity for students to apply their knowledge and understanding of modeling addition and subtraction problems on a number line diagram to a real-life situation. Students are asked to write equations and draw number line diagrams to solve a problem with a multi-step solution.

Key Concept students will use:

- We can use a number line to solve many types of addition and subtraction problems.

Skills students will use:

- create an addition or subtraction equation with an unknown to represent a problem situation (Grade 1, Unit 18)
- model addition and subtraction using a number line diagram

Students engage in Mathematical Practice 7 (Look for and make use of structure) as they look for number patterns and relationships on the number line to develop computational strategies.

**Key vocabulary: **

- addend
- compare
- number line diagram
- unknown

**Special materials needed:**

- blank number line diagrams (optional)