Math question

The area of the semi-circle is 157.00 cm square.

Let P = pi = 3.14
Let r = radius

perimeter of full circle = 2Pr (ie., 2 x P x r (read "Two-Pi-R"))
perimeter of semi-circle = (perimeter of a full circle)/2 + 2r = 51.4 cm
perimeter of semi-circle = (2Pr)/2 + 2r = Pr + 2r = (P+2)r = 51.4 cm
=> r = 51.4 cm / (P+2) = 51.4 cm / (3.14 + 2) = 10 cm

=>Area of semi-circle = (Area of a full circle) / 2 = (Prr) / 2 = P(10 cm)(10 cm)/2 = P(100 cm sq)/2 = 50P cm sq = 50 x (3.14) cm sq = 157.00 cm sq

1. circle area equation = radius ^2 x pi
2. radius x 2 x pi = perimeter

radius = (perimeter / pi) / 2

radius = 51.4 / 3.14 /2
= 8.18
put 2 into 1
therefore
circle area = 8.18 ^2 x pi
= 210 cm square

while that is a semi-circle
we need over 2

semi-circle area = 210 /2
= 105 cm square