Understand that attributes belonging to a category of two-dimensional figures also belong to all subcategories of that category.
For example, all rectangles have four right angles and squares are rectangles, so all squares have four right angles.
Students will practice naming triangles by their angles. Issue a set of the What’s Your Triangle Angle cards to each group. Tell students that each set of cards show the measures of the angles of triangles. When called on, the group classifies the kind of triangle when naming the triangle by its angles. Inform students that they need to add up all three angles measures to determine if the sum of the measures equal 180⁰; If the sum of the measures is not equal to 180⁰, the figure is not a triangle. Call on groups randomly to name the triangle for a specified set of cards. After each group identifies the kind of triangle, have them explain why it is that kind of triangle. Such as, the measure of all three angles are acute that is why it is an acute triangle.