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 1100 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?

Can someone please help me with a formula to use on this question?

Question

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 1100 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? 

Can someone please help me with a formula to use on this question?

anonymous · Answer

well the first question is to find the perimeter of the semi-circle, and the second part is to find the area of the semi-circle

anonymous · Answer

do you know the formula of the circumference of the circle

anonymous · Answer

oh yeah, draw a picture! :D

anonymous · Answer

is it pir^2?

anonymous · Answer

there is no need to find the area..

anonymous · Answer

circumference of a circle:  2*pi*r

anonymous · Answer

can you do it know?

anonymous · Answer

the area is necessary to calculate the enclosed area in acres.

anonymous · Answer

HOW MANY FEET ARE THERE IN AN ACRE?

anonymous · Answer

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anonymous · Answer

there are 
$$43560 ft^{2} = 1 acre$$
which are units of area.
check on google.

anonymous · Answer

YEAH, I DIDN'T READ THE SECOND QUESTION.. :D

anonymous · Answer

:D