#### Answer

$4$ meters

#### Work Step by Step

A square with area $18$ square meters will have side lengths that are the square root of the area. This is because, for a square, Area = $s^2$, so $s=\sqrt A$
With an area of 18 meters squared, $s=\sqrt {18}$. We will use method 2 in the book to estimate the square root.
According to a calculator's square root function, $\sqrt {18}\approx4.24$ meters
Since $4.24$ is closer to $4$ than to $5$, we round to the nearest integer which is $4$ meters.