Lesson objective: Develop and use the area formula for triangles.

This lesson helps to build procedural skill with finding the area of triangles. Coordinate grids are used here because they support the students' budding understanding of geometry in the coordinate plane. This work develops students' understanding that it is possible to find the area of a figure by creating a new region of known or equal parts.

Students engage in Mathematical Practice 7 (Look for and make sense of structure) as they begin to understand the relationships between the two-dimensional figures more completely.

**Key vocabulary:**

- area
- triangle

**Special materials needed:**

- coordinate grid