Students start the first lesson of the school year by recalling what they know about area (note that students studied the areas of rectangles with wholenumber side lengths in grade 3 and with fractional side lengths in grade 5). The mathematics they explore is not complicated, so it offers a low threshold for entry. The lesson does, however, uncover two important ideas:
 If two figures can be placed one on top of the other so that they match up exactly, then they have the same area.
 The area of a region does not change when the region is decomposed and rearranged.
At the end of this lesson, students are asked to write their best definition of area. It is important to let them formulate their definition in their own words. For English learners, it is especially important that they be encouraged to use their own words and also to use words of their peers. In the next lesson, students will revisit the definition of area as the number of square units that cover a region without gaps or overlaps.
As the first set of problems in a problembased curriculum, students will also begin their yearlong work on making sense of problems and persevering in solving them (MP1). This opening lesson leaves space for teachers to begin setting classroom routines and their expectations for mathematical discourse (MP3).
In all of the lessons in this unit, students should have access to their geometry toolkits, which should contain tracing paper, graph paper, colored pencils, scissors, and an index card. Students may not need all (or even any) of these tools to solve a particular problem. However, to make strategic choices about when to use which tools (MP5), students need to have opportunities to make those choices. Apps and simulations should supplement rather than replace physical tools.
Notes on terminology. In these materials, when we talk about a figure such as a rectangle, triangle, or circle, we usually mean the boundary of the figure (e.g., the sides of the rectangle), not including the region inside. However, we also use shorthand language such as “the area of a rectangle” to mean the “the area of the region inside the rectangle.” The term shape could refer to a figure with or without its interior. Although the terms figure, region, and shape are used without being defined precisely for students, help students understand that sometimes our focus is on the boundary (which in this unit will always be composed of black line segments), and sometimes it is on the region inside (which in this unit will always be shown in color and referred to as “the shaded region”).
Lesson overview
 1.1 Warmup: Which One Doesn’t Belong: Tilings (5 minutes)

1.2 Activity: More Red, Green, or Blue? (25 minutes)
 Includes "Are you Ready for More?" extension problem
 There is a digital applet in this activity.
 Lesson Synthesis
 1.3 Cooldown: What is Area? (5 minutes)
Learning goals:
 Recall the meaning of area.
Learning goals (student facing):
 Let’s look at tiling patterns and think about area.
Learning targets (student facing):
 I can explain the meaning of area.
Required materials:
 geometry toolkits
Required preparation:
 Assemble geometry toolkits.
 It would be best if students have access to these toolkits at all times throughout the unit.
 Toolkits include tracing paper, graph paper, colored pencils, scissors, and an index card to use as a straightedge or to mark right angles.
Glossary:
 area  The area of a twodimensional region, measured in square units, is the number of unit squares that cover the region without gaps or overlaps. The side length of each square is 1 centimeter. The area of the shaded region A is 8 square centimeters. The area of shaded region B is \(\frac12\) square centimeters.
 region  Examples of twodimensional regions include the interior of a circle or the interior of a polygon. Here are two examples of twodimensional regions. Area is a measure of twodimensional regions. Examples of a threedimensional region include the interior of a sphere or the interior of a cube.
 Access the complete Grade 6 glossary.
Adapted from Open Up Resources under CC BY license. All adaptations copyright LearnZillion.