A contractor has installed a silt fence around an area that is semi-circular and level to prevent soil from the construction site entering nearby streams. The diameter of the semi-circle is 900 feet. How many linear feet of fence does the contractor need to use to enclose the area? How many acres are within the enclosed by the fence? I need an answer for part two of the question.
Area of the whole circle is $\pi r^2=\pi 450^2$. For a semi circle it is $\pi 450^2/2$. In acres this is $\pi 450^2/(2*43560)=7.30$