Answer
The side length of the square is $9$ meter.
Work Step by Step
Let the side length of the square is $=a$.
Area of the square $A=81$ square meters.
Area formula for the square is
$\Rightarrow A=a^2$
Substitute $81$ for $A$.
$\Rightarrow 81=a^2$
Use $81=9^2$.
$\Rightarrow 9^2=a^2$
Take square root on each side.
$\Rightarrow 9=a$
Hence, the side length of the square is $9$ meter.
