It's in geometry.

Autumn -

Since a circle has 360 degrees, a 90 degree sector is 1/4 of the circle. Therefore, the area of the entire circle can be expressed as

Area of sector/Size of sector = Area of Circle/360

16 ft^{2}/90 = n/360

(360) (16 ft^{2})/90 = n

(4)(16 ft^{2}) = n

n = 64 ft^{2 }is the area of the entire circle.

Now since Area of a Circle = ∏r^{2},

∏r^{2} = 64

r^{2} = 64/∏

r = √(64/∏)

Rationalizing the denominator, we multiply by √∏/√∏ to get

r = √(64∏)/√(∏^{2}) and taking the square root of the denominator to get our answer of

r = √(64∏)/∏