Lesson objective: Define surface area and determine a strategy for finding the surface area of three dimensional figures from their nets.

Students bring prior knowledge of area of composite figures from CCSS 6.G.A.1. This prior knowledge is extended to surface area as students find composite areas of nets. A conceptual challenge students may encounter is that surface area is a two-dimensional measure of a three-dimensional figure.

The concept is developed through work with nets, which allow us to see all of the faces of a three dimensional figure at once, and also through formulas used for finding the area of rectangles and triangles.

This work helps students deepen their understanding of operations because students will use multiplication, addition, and area formulas in calculating surface area; it will also deepen their understanding of equivalence because nets are another way of representing three dimensional figures.

Students engage in Mathematical Practice 4 (Model with Mathematics) as they use nets of pyramids and prisms to make connections between two dimensional shapes and three dimensional figures. Students also engage in Mathematical Practice 7 (Look for and Make Use of Structure) as they use nets to determine surface area and how surface area relates to three dimensional figures.

**Key vocabulary:**

- area
- composite area
- composite figure
- net
- square units
- surface area
- three dimensional figure
- two dimensional shape