The radius of a circle is $14$ cm and the area of a square equals the area of the circle. The side of the square is approximately —

Setting the square's area equal to the circle's, $a^{2}=\pi r^{2}=\pi\times 14^{2}\approx 615.75$, so $a=\sqrt{615.75}\approx 24.81$ cm. Equal areas mean the side is the square root of the circle's area.