<PRE><B>Question 820395</B>
p=2*pi*r for a full circle

p=pi*r since it is only a semi circle
57=pi*r
r=57/pi
r = 18.144
the inner arc of the driveway has  a radius that is 12 feet shorter.
or about R=6.144

area of larger minus area of smaller= area of driver
1/2*pi*r^2 since it is a semi circle.
area=1/2 *pi*(57/pi)^2-1/2*pi*((57-12pi)/pi)^2=457.8

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