First, draw a diagram to visualize the situation:
The area of the region covered with small rocks can be found by subtracting the area of the circle from the area of the square.
The area A_s of a square with side L is given by:
![A_s=L^2](https://img.qammunity.org/2023/formulas/mathematics/college/nl0xusgg7lmoigmc2nfc3b5einrjhsaonx.png)
And the area A_c of a circle with radius r is given by:
![A_c=\pi r^2](https://img.qammunity.org/2023/formulas/mathematics/college/zkt0g16kohfatem6fclmlzw4rfyx1cl8z7.png)
Replace r=4ft and L=10ft into the equations to find the area of the circle and the square:
![\begin{gathered} A_s=(10ft)^2=100ft^2 \\ A_c=\pi(4ft)^2=16\pi ft^2\approx50.265ft^2 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/8j497x74pom93iu8fsnuczjx49n7m1tz3s.png)
Finally, subtract the area of the circle from the area of the square to find the area of the region covered with rocks:
![A=A_s-A_c=100ft^2-16\pi ft^2\approx49.7ft^2](https://img.qammunity.org/2023/formulas/mathematics/college/4y8n8ozl588z4wgy64uivcvtz9kex989l3.png)
Therefore, the area of the region covered with rocks is exactly 100-16π square feet, which is approximately equal to 49.7 square feet.