Using the triangle area formula (area = base × height / 2), the top figure has an apparent area of 32.5. But the individual components have an area that sums to 32. This means the top figure does not form a true triangle. The covered area of the top figure is 0.5 unit smaller than the apparent triangle. With the missing square the bottom figure has an area 0.5 unit larger. This gives a one unit difference which accounts for the empty square.