Question 234482
Area=pir^2=3.14*(100/2)^2=3.14*50^2=3.14*2,500=7,850 yds.^2 
2*7,850=pir^2
15,700=3.14*r^2
r*2=15,700/3.14
r^2=5,000
x=sqrt5,000
x=70.71 yds. is the total radius of the island & the moat.
Width of the moat=50+x=70.71=20.71 yds. is the width of the moat.
Answer A)