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
then find the fraction
84pi times (150/360)=35pi square inches
