The area of a square is determined by [tex]s^2[/tex] where s is the side length. Therefore we need to get the square root of [tex]16cm^2[/tex]. Notice that 16 is a square number so we can express it as 4^2.
[tex]s= \sqrt{4^2cm^2} =4cm[/tex]
Since we have an exponent of 2 and we are looking for the square root which is equivalent to the exponent [tex] \frac{1}{2} [/tex], we cancel both. Therefore the side length is 4 cm.