# Lesson 8

Sort Triangles

### Lesson Purpose

### Lesson Narrative

The purpose of this lesson is to sort triangles into categories, recognizing right triangles as a category. Students also examine side lengths and notice that sometimes all 3 side lengths are different, sometimes 2 side lengths are equal, and sometimes all 3 side lengths are equal. Students identify right triangles and examine the possible angles that a triangle can have. For example, there are triangles with 3 acute angles but a triangle can only have one right or obtuse angle. Students should have access to straight edges, protractors, and patty paper throughout this lesson.

- Engagement

- MLR7

### Learning Goals

Teacher Facing

- Classify triangles based on angle measurements and side lengths.

### Student Facing

- Let’s sort triangles.

### Required Materials

Materials to Copy

- Card Sort Triangles (Grade 5)

### Required Preparation

Activity 1:

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

Activity 2:

- Gather materials from previous activity:
- Triangle Cards

### Lesson Timeline

Warm-up | 10 min |

Activity 1 | 20 min |

Activity 2 | 15 min |

Lesson Synthesis | 10 min |

Cool-down | 5 min |

### Teacher Reflection Questions

### Suggested Centers

- Which One? (K–5), Stage 7: Grade 5 Shapes (Addressing)
- How Are They the Same? (1–5), Stage 5: Grade 5 Shapes (Addressing)
- How Are They the Same? (1–5), Stage 4: Grade 4 Shapes (Supporting)

### Print Formatted Materials

Teachers with a valid work email address can click here to register or sign in for free access to Cool Down, Teacher Guide, and PowerPoint materials.

Student Task Statements | docx | |

Lesson Cover Page | docx | |

Cool Down | Log In | |

Teacher Guide | Log In | |

Teacher Presentation Materials | docx | |

Blackline Masters | zip |