Consider the top left triangle which is isosceles right triangle ( 4, 4 and the hypotenus).
For any isosceles right triangle, the sides are in the ratio of 1 : 1 : square root of 2, Therefore The hypotenuse will be 4 * square root of 2.
This hypotenuse is also side of the inner square. Thereby the radius of the circle will be half of 4*sq. root of 2.
Meaning Radius = 2*sq.root of 2.
Area of circle = 22/7 (pai) * (radius square)
= (22/7)*4*2 = 25.143 sq.m