Begin the class by reviewing triangles. You may ask questions such as:
- What is a triangle?
- How can we classify triangles based on their sides?
- How can we classify triangles based on their angles?
- Using different quadrilaterals, how can you cut or fold paper to create triangles?
Distribute the Just Two Triangles activity sheet to each student.
Have students cut out two triangles from the activity sheet.
Use the models of the square, triangle, and parallelogram to encourage students to make various shapes. Ask them to try to make these shapes with two triangles. Have the students glue the "new" shapes onto the activity sheet.
In a whole-class discussion, encourage students to share at least one important thing that they noticed about one of the new shapes: likenesses and differences; where it could be seen
in the classroom, playground, school, or at home; and so on.
Some possible drawings for the activity sheet include:
Next, investigate building three-dimensional shapes with triangles. You will need to duplicate the triangles on heavy paper. Students may discover three-dimensional figures created from triangles, which may include triangular pyramids and triangular prisms.
