It can be seen from the pictures on the left that three triangles cover the same area as one square and one triangle (two half triangles). So that means that the square has the same area as two triangles, or an area of 2. From the pictures on the right it can be seen that a square and a triangle have the same area as two skinny rhombi and a triangle. Because both pictures have a triangle in them it means that the remaining shapes must have the same area. So, the square has the same area as two skinny rhombi - and because a square has an area of 2 then skinny rhombus has an area of 1.