Matthew sorted these shapes into two groups. How did he sort these shapes? By number of vertices or corners, by colour, or by size.
Let’s test the first option by number of vertices or corners. How many vertices do the shapes in this group have? Let’s count them. This rectangle has one, two, three, four. The square has four corners or vertices and so does the big square. And the pink rectangle also has four vertices. So we could call this group “shapes with four vertices.”
How many vertices do the shapes in this group have? Let’s count them. There are three. Each of the triangles in this group has three vertices. So we could name this group “shapes with three vertices.”
As the shapes are all different colours, they haven’t been sorted by colour. And they are also different in size. So they haven’t been sorted by size. These shapes have been sorted by the number of vertices.