Students will discover through this activity that the angles of triangles always add up to 180 degrees. The teacher will need to print out enough of each of the three types of triangles so each student has one of each. Students will tear off the corners of one of the triangles and arrange the corners on the straight line to show that the sum of the angles equals a straight line or 180 degrees. They will then glue the torn triangle on top of the matching triangle. They will repeat the process for the other two triangles. They then fill in the graphic organizer.