Third graders learn the two rules that make a shape a polygon, closed and made of straight sides, and sort familiar shapes into polygons and not polygons.
Students will be able to…
A triangle is a polygon and a circle is not, even though both are shapes. What are the two rules that decide whether a shape is a polygon?
Project this and sort each shape into polygon or not a polygon — tap a shape, then tap where it belongs.
Tap any phase to open the teacher moves and student actions.
A triangle is a polygon, but a circle is not. Both are shapes, so what is the rule that lets one in and keeps the other out?
Students sort shapes into polygons and not polygons.
Students name polygons by their sides.
Students find polygons around them.
Students reflect on polygons.
Aligned to the Common Core State Standards for Mathematics (Grade 3).
Understand that shapes in different categories may share attributes and that shared attributes can define a larger category, such as quadrilaterals.
Recognize and draw shapes having specified attributes; identify triangles, quadrilaterals, pentagons, and hexagons.
Classify two-dimensional figures based on the presence or absence of lines or angles of a specified type.
Attend to precision.
Preview the three formative checks. Tap “Sample answer” to see what mastery looks like — hide them before you print for students.
Have students look around the room, find three polygons, and name each one by its number of sides, so the definition connects to the real world. A printable polygons worksheet is in the Mathematics library.
Tap a card to flip it, then rate whether you knew it. Built from this lesson’s vocabulary.
A quick self-check with instant feedback, drawn from this lesson’s key terms.
A print-and-go review sheet with a built-in answer key. Tap “Show answer key” to reveal answers, or print the clean version for students.