Illustrative Mathematics
Are These Right?
Is that a right triangle or a wrong triangle? Young mathematicians look at eleven different shapes and use a measuring tool of their choice to determine which triangles have right angles. Consider cutting out sets of the shapes to...
Curated OER
Attributes of Shapes Guided Lesson Explanation
Triangles, circles, and rectangles are featured in a colorful, one-page learning exercise that defines and illustrates these shapes. Read the explanations with your first graders and have them count the number of shapes in a given box....