2D Shapes and PerimeterAttributes of 2D Shapes

In third grade, students see that quadrilaterals can be classified based on their sides (whether some are of equal length) and their corners (whether one or more square corners are present). They sort shapes using language and attributes that are familiar to them.

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Quadrilaterals can be used to create patterns that are visually appealing and interesting. Look at how the pattern changes as we highlight the shapes in the design:

A quadrilateral consists of 4 1 2 3 sides and 4 1 2 3 corners. Students come to understand that a shape can have more than one name.

A rectangle is a quadrilateral with equal angles:

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A square is a quadrilateral with equal sides and angles:

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A rhombus is a quadrilateral with equal sides.

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Students also see that some quadrilaterals aren’t squares, rhombuses, or rectangles because they don’t have the defining attributes of these shapes.

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For example, here are three quadrilaterals. The first one is a rectangle, a rhombus, and a square. The other two are not are squares, rhombuses, or rectangles.

Here are two more examples:

It is True False that both shapes are quadrilaterals.

It is False True that both shapes have one or more square corners.

It is False True that both shapes have two equal-side lengths.