# Lesson 5

Some Triangles, All Triangles

## Warm-up: Which One Doesn’t Belong: Shapes (10 minutes)

### Narrative

This warm-up prompts students to compare four two-dimensional shapes. It gives students a reason to use language precisely (MP6). It gives the teacher an opportunity to hear how students use informal and formal language to talk about characteristics of the items in comparison to one another. During the synthesis, ask students to explain the meaning of any terminology they use, such as curved and open.

### Launch

• 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

### Activity

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

### Student Facing

Which one doesn’t belong?

### Activity Synthesis

• “Let’s find at least one reason why each one doesn’t belong.”

## Activity 1: Triangles and “Not Triangles” (10 minutes)

### Narrative

The purpose of this activity is for students to analyze examples and non-examples of triangles. As students compare examples and non-examples, they identify and articulate the defining attributes of triangles (MP6).

MLR8 Discussion Supports. Before students share, remind them to use words such as sides, corners, straight, and pointy.
Representation: Internalize Comprehension. Synthesis: Provide more examples and non-examples to reinforce the defining attributes of triangles.
Supports accessibility for: Conceptual Understanding, Visual-Spatial Processing

### Required Materials

Materials to Gather

### Required Preparation

• Each group of 2 needs a set of Flat Shape Cards from a previous lesson.

### Launch

• Groups of 2
• Display the first question.
• “Here are four triangles. What do all of these triangles have in common?” (They all have three sides and three corners. They are all pointy. They are all closed.)
• 30 seconds: quiet think time
• “Share your thinking with your partner.”
• 2 minutes: partner discussion
• Share responses.
• If a student shares that all the triangles are white, ask, “If I colored one of these shapes in red, would it still be a triangle?”

### Activity

• Read the second question.
• “Work with your partner to think of what makes these ‘not triangles’ different from the triangles in the first problem.”
• 3 minutes: partner discussion

### Student Facing

1. These are triangles.

What is the same about all these triangles?

2. These are not triangles.

What makes these shapes different from the triangles?

### Activity Synthesis

• “What makes the triangles different than the 'not triangles'?”
• Give each group a set of shape cards from previous lessons.
• “Work with your partner to sort your shape cards into the categories of ‘triangles’ and ‘not triangles.’”
• Share responses.

## Activity 2: Draw Triangles (10 minutes)

### Narrative

The purpose of this activity is for students to draw triangles. Students use dot paper to draw triangles and then draw shapes that are not triangles. Students may use the shape cards to visualize and draw shapes.

### Required Materials

Materials to Gather

Materials to Copy

• Centimeter Dot Paper - Standard

### Required Preparation

• Each group needs a set of Flat Shape Cards from the previous activity.

### Launch

• Groups of 2
• Give each group a set of flat shape cards and two pieces of dot paper.
• “Choose three dots. Connect the dots.”
• 30 seconds: independent work time
• “Compare your drawing with your partner. What do you notice?” (We both drew triangles. The triangles are different sizes. They both have three sides.)
• 1 minute: partner share
• Share responses.

### Activity

• “Use the dot paper in your book to draw three triangles and three shapes that are not triangles. You may use the shape cards to help you.”
• 6 minutes: independent work time
• Monitor for some triangles and 'not triangles' to share during the lesson synthesis.

### Student Facing

1. Draw 3 different triangles.

2. Draw 3 different shapes that are not triangles.

### Activity Synthesis

• “Who thinks they drew a triangle that no one else drew?”
• Invite students to share their shapes and explain how they know they are triangles.

## Activity 3: Centers: Choice Time (20 minutes)

### Narrative

The purpose of this activity is for students to choose from activities that offer practice adding and subtracting or working with shapes. Students choose from any stage of previously introduced centers.

• Geoblocks
• How Are They the Same
• Compare
• How Close

### Required Materials

Materials to Gather

### Required Preparation

Gather materials from previous centers:

• Geoblocks, Stage 3
• How Are They the Same?, Stage 1
• Compare, Stage 1
• How Close, Stages 1-3

### Launch

• Groups of 2
• “Now you are going to choose from centers we have already learned.”
• Display the center choices in the student book.
• “Think about what you would like to do first.”
• 30 seconds: quiet think time

### Activity

• Invite students to work at the center of their choice.
• 8 minutes: center work time
• “Choose what you would like to do next.”
• 8 minutes: center work time

### Student Facing

Choose a center.

Geoblocks

How Are They the Same?

Compare

How Close?

### Activity Synthesis

• “How did you decide which centers to choose today?”

## Lesson Synthesis

### Lesson Synthesis

“Today we looked at shapes that are triangles and shapes that are not triangles. Then we drew our own shapes.”

Display shapes drawn in a previous activity. “How can we tell if these shapes are triangles or not?” (If they are triangles they will have three sides, three corners, the sides will be straight and the shapes will be closed.)