The area of a square is given by:
[tex]A=l^2[/tex]By solving for l you get:
[tex]l=\sqrt[]{A}[/tex]In this case A = 320 ft^2.
[tex]\begin{gathered} l=\sqrt[]{320ft^2} \\ l=17.88ft \\ l\approx18ft \end{gathered}[/tex]Hence, the length of one side of the square floor is approximately 18 ft