Given the circumference of the semicircle, the formula of area

Given the circumference of the semicircle, the formula of area

Because the circumference of the semicircle is C = π R + 2R = (π + 2) r
So r = C / (π + 2)
So the area is s = π R ^ 2 = π * [C / (π + 2)] ^ 2

Known that the circumference of a semicircle is 128.5, seek his floor area!

Let R be the radius
Then the half circle is 3.14r
Two radii are added to the circumference of the semicircle
So 3.14r + 2R = 128.5
r=128.5÷5.14=25
So area = 3.14 × 25 × 25 △ 2 = 981.25

The circumference of the semicircle is 51.4cm, and its area is______ Square centimeter

The radius of semicircle is: 51.4 △ 3.14 + 2, = 51.4 △ 5.14, = 10 (CM); so the area of semicircle is: 3.14 × 102 △ 2 = 157 (square cm); answer: its area is 157 square cm. So the answer is: 157