+129849 Area of innermost red area = pi (2/2)^2 = pi units^2
Area of next red area = pi [ (6/2)^2 - (4/2)^2 ] = pi [ 3^2 - 2^2 ] = 5 pi units^2
Area of last red area = pi [ (10/2)^2 - (8/2)^2 ] = pi [ 5^2 - 4^ 2 ] = 9pi units^2
So....the total of the red areas =
pi [ 1 + 5 + 9 ] =
15 pi units^2
