Explanation:
the area of the shaded region is the area of the main square minus the area of the circle.
the area of the square is
16×16 = 256 cm²
the area of the circle is (r or radius = half of the side length of the square)
pi×8² = pi×64 = 201.0619298... cm²
the shaded area is then
256 - 201.0619298... = 54.93807017... cm²