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Area of whole circle = pi r^2       this is 1/4 of this    1/4 pi r^2

 

Whole circumference = pi d       this is 1/4 of this   1/4 pi d = 2 pi

                                                                                d = 8             so r = 4

 

Area = 1/4 pi r^2  =  1/4 pi (4^2) =..........