Team Triangles

Solal Stern

Tier 2

Lesson Plan

Team Triangles Warm-Up Plan

Students will collaboratively review and apply perimeter calculation by racing to build triangles that match given perimeters, practicing turn-taking and providing positive feedback.

This lesson reinforces key geometry skills (perimeter) while integrating social-emotional learning through cooperative problem solving, promoting teamwork habits and confidence in math.

Audience

5th Grade Students

Time

20 minutes

Approach

Team-based triangle assembly races with guided reflection

Materials

Perimeter Refresher Slides, - Triangle Builders Kit, - Math & Manners Prompt, and - Reflection Exit Slip

Prep

Prepare Materials

5 minutes

Review the Perimeter Refresher Slides to select perimeter values.
Gather and organize all components in the Triangle Builders Kit.
Print sufficient copies of the Math & Manners Prompt and Reflection Exit Slip.
Arrange desks into teams of three for easy collaboration.

Step 1

Warm-Up – Math & Manners

5 minutes

Display the Math & Manners Prompt.
Discuss expected teamwork behaviors and respectful math talk.
Pose two quick perimeter review problems from the Perimeter Refresher Slides.
Model turn-taking and positive feedback phrases.

Step 2

Team Triangle Challenge

12 minutes

Divide students into teams of three and distribute the Triangle Builders Kit.
Reveal a perimeter value from the Perimeter Refresher Slides.
Teams work together to assemble a triangle whose side lengths sum to the given perimeter.
Each student takes one turn placing a strip and offers positive feedback to a teammate.
Circulate to check calculations and reinforce collaboration skills.

Step 3

Cool-Down – Reflection Exit Slip

3 minutes

Distribute the Reflection Exit Slip.
Students write one perimeter strategy they used and one way they supported their teammates.
Collect slips as students leave to inform future instruction.

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Slide Deck

Perimeter Refresher

Perimeter = the total distance around a shape.

For polygons, add the lengths of all sides.

Introduce the concept of perimeter to students. Emphasize that perimeter measures the distance around a shape.

Perimeter Formula for Triangles

For any triangle with side lengths a, b, and c:

P = a + b + c

Example:
• a = 3 cm, b = 4 cm, c = 5 cm
• P = 3 + 4 + 5 = 12 cm

Point out the formula for triangles specifically and model writing the formula on the board.

Example Problem

Triangle with sides 6, 7, and 5 units:

P = 6 + 7 + 5 = 18 units

Work through this example step-by-step. Ask students to call out each addition.

Quick Practice

Calculate the perimeter of each triangle:

Sides: 4, 4, 4
Sides: 5, 8, 3
Sides: 2, 9, 6

Have students solve these mentally or on scratch paper, then share answers.

Challenge Prompts

In our Team Triangles game, you may see these target perimeters:
• 12 units
• 15 units
• 18 units
• 21 units

Explain that these are example perimeters students will see in the Team Triangles game. Teams will choose side-length strips to match these totals.

Triangle-Building Reminder

To form a valid triangle, the sum of any two sides must be greater than the third side.

For example: 3 + 4 > 5, 4 + 5 > 3, 3 + 5 > 4

Remind students of the triangle inequality so their shapes will close properly.

Game

Triangle Builders Kit

A hands-on game kit designed for the Team Triangles challenge. Students use side-length strips, draw target perimeter cards, and earn positive feedback tokens as they work cooperatively to build valid triangles.

Contents:
- 50 side-length strips (lengths 2–10 units; five of each length)
- 20 target perimeter cards (perimeters: 12, 15, 18, 21 units; five of each)
- 30 positive feedback tokens (smiley faces)
- 6 team mats (for groups of three)
- 1 Instruction Sheet

Setup:
1. Shuffle and spread side-length strips in the center of the table.
2. Shuffle target perimeter cards face-down.
3. Give each group one team mat.
4. Place feedback tokens within reach.

How to Play:
1. A student draws a target perimeter card and reads the value aloud.
2. In turn, each team member selects one strip that they believe helps reach the target when combined with the other two strips.
3. After each pick, teammates add up the side lengths and check the triangle inequality to ensure a valid shape.
4. Once three strips are chosen, assemble them on the team mat to form a triangle.
5. If the total equals the target perimeter and the triangle inequality holds, the round is a success. The team keeps the card and each member earns a feedback token.
6. Teams give each other positive feedback using the tokens, then shuffle used cards and strips before drawing a new card for the next round.

Enjoy racing to build accurate triangles while practicing math skills and teamwork!

Warm Up

Math & Manners Prompt

1. Teamwork Expectations
When we work together in math, we:
• Listen carefully when someone explains their thinking.
• Speak respectfully and encourage each other.
• Take turns and share ideas.

Write one example of positive feedback you can give a teammate:

2. Respectful Math Talk
Fill in the blank:
"I like the way you __________ because __________."

3. Quick Perimeter Review
Calculate the perimeter of each triangle below.
a) Sides: 3, 4, 5
P = ________ units

b) Sides: 6, 7, 5
P = ________ units

Cool Down

Reflection Exit Slip

1. What perimeter strategy did your team use to reach the target perimeter?

2. Describe one way you supported your teammates during the challenge.