Perseus best proves he is a hero with great fighting skills by

Perseus, the son of Danaë and Zeus, is famous for his bravery and fighting skills which he demonstrated in several mythological passages, but two events stand out: the slaying of Medusa (who could turn men into stone), the only one of the Gorgon sisters that was mortal, and the slaying of the sea serpent that was terrorizing the people of Aethiopia, and saving, in the way, the life of the beautiful Andromeda who he would later marry.  

to inform the reader that the text will take a second look at the grimms’ original tales

the answer is

r ≈5.641

plug in the area of 100 yards into the equation

100=

divide each side by pi

≈ 31.8309=

take the square root of each side to find r

=r

r ≈5.641