Question 1141716
The circle has radius 5 cm for an area of 25*pi mm^2.
If one draws this, a right triangle may be formed with one leg the radius of the circle, the second leg 1/2 the side of the square, and the hypotenuse half the diagonal of the square.
Because that triangle is a 45-45-90 triangle, half the side of the square is 5 cm as well and the area of the square is 100cm^2, (10 cm)^2.