Question 1067676
I'm assuming the main disk is 14 inches in diameter.
The Area is 49 pi, subtracting pi and also 4 pi
so 5 pi/49 pi is subtracted, or 10.20 per cent.  The net area is 44 pi.  By keeping pi as an irrational number, no rounding needs to be done until the end.  Your work is otherwise appropriate, given what I am visualizing.