The insides of this square is now made up of a 2 by 2 square in the center, surrounded by 4 triangles with bases of 3 units and heights of 1 unit. The formula for the area of a triangle is bh/2, which means that each triangle had an area of 1.5. Multiplying this by 4 and adding the area of the central square, you get a total area of 4+6=10. Hope this helps!
