# Lesson 3

### Lesson Purpose

The purpose of this lesson is for students to classify quadrilaterals by the size of their angles, the length of their sides, and the presence of parallel and perpendicular sides.

### Lesson Narrative

In the previous lesson, students sorted and analyzed triangles by their sides and angles and began to form general statements about the properties of triangles. (Triangles always have three sides and angles, may have a right angle or equal sides, may be foldable into equal halves, never contain more than one obtuse angle, and so on.)

In this lesson, students identify and sort quadrilaterals based on their angles and sides, including whether their sides are parallel. Students are introduced to the term parallelogram to describe quadrilaterals with two pairs of parallel sides, but they are not expected to use this term throughout the unit. In grade 5, students will continue the work of classifying polygons using these categories.

• Engagement
• MLR8

### Learning Goals

Teacher Facing

• Classify quadrilaterals based on the length of their sides, the size of their angles, and prescence of parallel sides.

### Student Facing

• Let’s sort and identify quadrilaterals.

### Required Preparation

Activity 1:

• Each group needs a set of shape cards from the previous lesson. If time permits, separate the quadrilateral cards from each set in advance.

Activity 2:

• Each group needs a set of shape cards from the previous activity.

### Lesson Timeline

 Warm-up 10 min Activity 1 20 min Activity 2 15 min Activity 3 10 min Lesson Synthesis 10 min Cool-down 5 min

### Teacher Reflection Questions

Who participated in math class today? How can you leverage each of your students’ ideas to support them in being seen and heard in tomorrow’s math class?

### Suggested Centers

• Which One? (K–5), Stage 4: Grade 3 Shapes (Supporting)
• Can You Draw It? (1–5), Stage 4: Area and Perimeter (Supporting)

### Print Formatted Materials

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