# Lesson 5 Some Triangles, All Triangles

Let’s explore what makes a shape a triangle.

## Warm-up Which One Doesn’t Belong: Shapes

Which one doesn’t belong?

## Activity 1 Triangles and “Not Triangles”

These are triangles.

What is the same about all these triangles?

These are not triangles.

What makes these shapes different from the triangles?

## Activity 2 Draw Triangles

Draw 3 different triangles.

Draw 3 different shapes that are not triangles.

## Activity 3 Centers: Choice Time

Choose a center.

Geoblocks

How Are They the Same?

Compare

How Close?

## Practice Problem

## Problem 1

Is this shape a triangle? Why or why not?