Lesson 18

This warm-up prompts students to compare four images. It gives the teacher an opportunity to hear how students use terminology and talk about characteristics of the items in comparison to one another. 

In the synthesis it is important to discuss things the writer had to pay attention to when they designed this activity.

• Groups of 2
• Display the image.
• “Pick one that doesn’t belong. Be ready to share why it doesn’t belong.”

• 1 minute: quiet think time
• 2–3 minutes: partner discussion
• Record responses.
   

• “What did the writer of this activity have to pay attention to when they designed this activity?” (the number of sides, the types of angles or corners, the way they were oriented, how many shapes there were in each)
• “Where do we see those things in our reasons for which one didn’t belong?”
• Record and display responses for all to see.

The purpose of this activity is for students to reason about attributes of three-dimensional shapes including side lengths and volume. Students select a few shapes from premade cards and create their own to complete a Which One Doesn’t Belong activity. If there is time, students can facilitate their Which One Doesn’t Belong with another group.

• Create a set of cards from the blackline master for each group of 2. 

• Groups of 2 or 4
• “Now you will work with your group to complete a Which One Doesn’t Belong activity. You will select three shapes from the set of cards and create one shape on your own. Discuss why the shapes you select and draw do not belong.”

• 10 minutes: small-group work time
• As students work, monitor for groups who discuss and design an image based on some of the following:
  • the volume of the shape: 12, 20, or 27 cubic units
  • if the shape is a rectangular prism or a figure composed of rectangular prisms
  • the side lengths of the shape
  • if the cubes are visible or not

• Choose small groups to share the different reasons the shapes they chose or drew do not belong. 
• Ask students to share their completed Which One Doesn’t Belong and ask the class to share reasons the images do not belong.
• As each group shares, continually ask others in the class if they agree or disagree and the reasons why.

The purpose of this activity is for students to reason about attributes of three-dimensional shapes including side lengths and volume. Students select two shapes from premade cards and create their own to complete a Which One Doesn’t Belong activity. If there is time, students can facilitate their Which One Doesn’t Belong with another group.

• Groups of 2 or 4
• “Now you will work with your group to complete a Which One Doesn’t Belong activity. You will select two shapes from the set of cards and create two shapes on your own. Discuss why the shapes you select and draw do not belong.”

• 10 minutes: small-group work time
• As students work, monitor for groups who discuss and design an image based on some of the following:
  • the volume of the shape: 12, 20, or 27 cubic units
  • if the shape is a rectangular prism or a composite
  • the side lengths of the shape
  • if the cubes are visible or not

• Choose small groups to share the different reasons the shapes they chose or drew do not belong. 
• Ask students to share their completed Which One Doesn’t Belong and ask the class to share reasons the images do not belong.
• As each group shares, continually ask others in the class if they agree or disagree and the reasons why.

The purpose of this activity is for students to design their own Which One Doesn’t Belong and describe the mathematical ideas they wanted others to notice in their images. If students struggle to decide on a focus of their design, it may be helpful to give them a topic such as “properties of shapes” or “fractions.”

• Groups of 2 or 4
• “Now you will work with your group to create your own Which One Doesn’t Belong. After you create your images, record the mathematical ideas you wanted others to notice.”

• 10 minutes: small-group work time
• As students work, monitor for groups who choose different areas of focus to share in the whole-group discussion.

• “What mathematical ideas did you want others to notice about the images you created?”
• As each group shares, continually ask others in the class if they agree or disagree and the reasons why.