The area of a square is given by the formula:

Where l is the length of its side. If the area is given, then the length can be calculated from that formula taking the square root to both sides of the equation. Then:
![l=\sqrt[]{A}](https://img.qammunity.org/2023/formulas/mathematics/college/vismzfwpkeq83sk5myikovx59utdujoojm.png)
Substitute A=225 to find the length of the square:
![\begin{gathered} l=\sqrt[]{225} \\ \Rightarrow l=15 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/cjdrm6g1o4ccqvjdgy9l7h200di8ra3nfx.png)