Let the side length of a square be x, then the radius of the largest circle in the square is X/2 of half the side length. Note: X/2 represents two thirds of x, and x 2 represents the square of X.

Because s is positive = x 2 = 80, s circle = 3.14× (x/2) 2 = 3.14× x2/4 = 3.14× 80/4 = 628 (square centimeter).