Unit 7
Two-Dimensional Shapes and Perimeter
Unit Goals
- Students reason about shapes and their attributes, with a focus on quadrilaterals. They solve problems involving the perimeter and area of shapes.
Unit Narrative
In this unit, students reason about attributes of two-dimensional shapes and learn about perimeter.
Students learn to describe, compare, and sort two-dimensional shapes in earlier grades. In this unit, students continue to develop language that is increasingly more precise to describe and categorize shapes. Students learn to classify broader categories of shapes (quadrilaterals and triangles) into more specific subcategories based on their attributes. For instance, they study examples and non-examples of rhombuses, rectangles, and squares, to recognize their specific attributes.
These are rectangles.
These are not rectangles.
Students also expand their knowledge about attributes that can be measured.
Previously, they learned the meaning of area and found the area of rectangles and figures composed of rectangles. In this unit, students learn the meaning of perimeter and find the perimeter of shapes. They consider geometric attributes of shapes (such as opposite sides having the same length) that can help them find perimeter.
Find the perimeter of this rectangle.
As the lessons progress, they consider situations that involve perimeter, and then those that involve both perimeter and area. These lessons aim to distinguish the two attributes (which are commonly confused) and reinforce that perimeter measures length or distance (in length units) and area measures the amount of space covered by a shape (in square units).
At the end of the unit, students solve problems in a variety of contexts. They apply what they learn about geometric attributes of shapes, perimeter, and area, to design a park, and a West African wax print pattern. They then solve problems within the context of their design.