Area of sector=fraction of sector times area of circle fraction of sector=degrees/360 and area of circle=pir^2
so hold a sec, we have the wiper on the outside, so we want to find the outside ring thing do area big sector-area small sector or even better (degrees/360) times (area big-areasmall) big is 10 small is 4 (10-6=4) areabig=10^2 times pi or 100pi areasmall=4^2 times pi or 16pi areabig-areasmall=100pi-16pi=84pi
What you have here is the fibonacci sequence. Each number in the sequence adds itself to the number before it. 1+1 = 2 1+2 = 3 3+2 = 5 5+3 = 8 8+5 = 13 the sequence is 0,1,1,2,3,5,8,13
