A landscape designer wants to include a semicircular patio at the end of a square sandbox she knows that the area of the semicircular patio is 25.12 cm squared

EXPLANATION
Let's see the facts:
The Area is 25.12cm^2
The Area of the circle is given by the following equation:
[tex]\text{Area}_{semicircle}=\frac{1}{2}\pi\cdot r^2[/tex]We need to isolate r in order to get the length of the side:
[tex]25.12=\frac{1}{2}\cdot\pi\cdot r^2[/tex]Dividing both sides by pi:
[tex]\frac{25.12}{\pi}=\frac{1}{2}r^2[/tex]Multiplying both sides by 2:
[tex]\frac{2\cdot25.12}{\pi}=r^2[/tex]Now, we need to apply the square root to both sides:
[tex]\sqrt[]{\frac{2\cdot25.12}{\pi}}=r[/tex]Switching sides:
[tex]r=\sqrt[]{\frac{50.24}{\pi}}=\sqrt[]{16}[/tex]Simplifying the square root:
[tex]r=4[/tex]The radius is r=4, but the diameter of the semicircle is equivalent to the side of the square so,
Side of square = Diameter of semicircle = 2*4 = 8
The answer is 8cm