Diameter of circle = length of each side of the square
The formula for calculating the area of a square is
Area = l^2
where l is the length of each side
From the information given,
Area = 900
900 = l^2
l = √900
l = 30
diameter = 30
radius = diameter/2 = 30/2
radius = 15
The formula for calculating the area of a circle is
Area = πr^2 = π * 15^2
Area of circle = 225π in^2