The diameter of the circle is 28 inches.
Given:
Area of a circle = 615.44 in²
Area of a circle is computed by multiplying pi and the radius raised to the 2nd power.
A = π r²
615.44 in² = 3.14 * r²
615.44 in² / 3.14 = r²
196 = r²
√196 = √r²
14 in = r
Diameter is twice its radius. So, d = 2r; d = 2 * 14 ; d = 28 inches