Lesson 3

This warm-up prompts students to notice the attributes of the parallelograms in a brick pattern. It gives the teacher an opportunity to hear how students use terminology from previous lessons to talk about parallel sides, angles, and side lengths.

• Groups of 2
• Display the image.
• “How many bricks have 2 pairs of parallel sides?”
• 1 minute: quiet think time

• “Discuss your thinking with your partner.”
• 2–3 minutes: partner discussion
• Record responses.

• “Which bricks have only one pair of parallel sides?” (Each brick that lays horizontally and is not triangular has one pair of parallel sides. The slanted bricks cut off by the edges of the image also have one pair.)
• “Do you think all figures with more than 3 sides have at least 1 pair of parallel sides?” (No, but this image does not show any examples. There are some figures with more than 3 sides with no pairs of parallel sides.)

In this activity, students analyze the sides and angles of quadrilaterals with attention to the presence of parallel and perpendicular lines. Students are given a set of shapes (a subset of the cards used in previous lessons) and prompted to look for quadrilaterals that have certain attributes. They also have an opportunity to propose an attribute for their partner to find, and make some general observations about the sides and angles of quadrilaterals.

In the synthesis, when discussing quadrilaterals with two pairs of parallel sides, introduce the term parallelogram. Students are not required to know the definition of this term at this point, however, and should not be assessed on it.

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

• Groups of 2
• Give each group a set of cards from the previous lessons.
• “Use only the cards with quadrilaterals for this activity.”

• “Complete the scavenger hunt with a partner and compare responses with another group.”
• 8–10 minutes: group work time on the first two questions
• Monitor for students who use tools to:
  • measure sides and angles
  • determine if two sides are parallel
• 2 minutes: individual work time on the last problem

Students may identify only one quadrilateral per attribute. Consider asking:

• “How did you make sure you found all the quadrilaterals that have each attribute?”
• “How would you check if a quadrilateral has only one of the attributes or more than one?”

• “Let’s use our arms to show what parallel lines look like.” (Students hold up two arms parallel to each other.)
• “How did you decide if the sides of a figure are parallel?” (Check if the distance between them is always the same. Extend the sides to see if the lines would eventually meet.)
• As needed, place a ruler between the extended arms of a student to illustrate checking for parallelism.
• “How did you know if any sides are perpendicular?” (Check if the sides make a right angle.)
• Ask students to share their completed sentences for the last question. Record their responses and invite the class to agree or disagree.
  • Some quadrilaterals . . .
  • All quadrilaterals . . .
  • No quadrilaterals . . .
• Explain to students that quadrilaterals with two sets of parallel sides are called parallelograms.
• Ask students to identify all the parallelograms in the set of cards. (D, K, N, U, Z, AA, EE, JJ)
• “We may know some of these figures by other names like rectangle or rhombus, but as long as the quadrilaterals have two pairs of parallel sides, they are also parallelograms.”

In this activity, students begin to formalize their understanding of the attributes of some shapes they have worked with since grades 2 and 3. Students use their observations from the previous activity to draw general conclusions about rectangles, squares, parallelograms, and rhombuses. The conclusions may be incomplete at this point.

Students are not expected to recognize that the attributes of one shape may make it a subset of another shape (for example, that squares are rectangles, or that rectangles are parallelograms). They may begin to question these ideas, but the work to understand the hierarchy of shapes will take place formally in grade 5. During the synthesis, highlight how sides and angles can help us define and distinguish various two-dimensional shapes.

When students describe the sides and angles in the shapes they use language precisely (MP6) and observe common structure in the different sets of quadrilaterals (MP7).

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

• Groups of 2
• Give each group a set of cards from the previous activity and a large sheet of paper for each shape (square, rectangle, rhombus, parallelogram).
• Provide access to rulers, protractors, and patty paper.
• “List 4–5 statements that are true for each set of quadrilaterals.”

• 5 minutes: group work time
• Rearrange students into groups of 3–4. Assign each group one set of quadrilaterals (squares, rectangles, parallelograms, or rhombuses).
• “In your new group, discuss the statements about the set assigned to you.”
• “Work together to create a poster that lists everything you found to be true for your set.”
• 3 minutes: group work time
• Consider allowing groups working on the same set to compare lists before the synthesis.

Students may wonder how shape AA and Z can belong to multiple groups. Invite students to make a “notice and wonder” chart to record their questions during the activity and to share them in the synthesis. Consider asking:

• “What did you say was true for all squares? For all rectangles? For all rhombuses?”
• “Does the shape you are wondering about have all of those attributes?”
• “Can you think of other shapes that have more than one name?”

• For each set of quadrilaterals, select one group to share their poster of statements. Invite other students to suggest amendments or corrections if they disagree.
• “Rectangles and parallelograms share many attributes. What makes them different?” (To be a rectangle, all angles must be equal or must be right angles.)
• “Rectangles and squares share many attributes. What makes them different?” (To be a square, all sides must have the same length.)
• “Rhombuses and squares share many attributes. What makes them different?” (To be a square, all angles must be equal or must be right angles.)

In this optional activity, students work with a partner to practice naming and looking for certain attributes in quadrilaterals. Each partner has a chance to select a particular attribute that a quadrilateral might have and to find examples and non-examples. Their partner must deduce the attribute they chose based on the examples and non-examples.

Students may choose familiar attributes—lengths of sides, presence of certain types of angles, parallelism, or perpendicularity—or pick a one that is much narrower or broader. In the synthesis, consider discussing how the specificity of an attribute affects the guessing process.

• Groups of 2
• Read the task statement as a class. Clarify the directions as needed.

• “Play two rounds of the guessing game with your partner. Switch roles for the second round. Write down the correct attribute at the end of each round.”
• If time permits, encourage students to play another round.

• Invite students to share the attributes they chose. Ask them to reflect on the process of deducing the attributes from examples and non-examples.
• “Was there an attribute that was particularly tricky to figure out? What about the examples and non-examples might have made it hard to guess?” (Students may say:
  • The examples had many attributes in common, likewise with the non-examples.
  • There are not enough examples in the set.
  • The attribute is very specific—for example, one angle that is greater than \(90^\circ\) but less than \(120^\circ\).)