Question

what is the area of a semicircle with a diameter of 40

Answer 1

pi * r^2 ...diameter = 40 therefore radius is 20 ....20^2 = 400 ...400 ...pi = 3.14....400 *3.14 = 1256

Answer 2

40 / 2 = 20 
20 = radius 

20 x 20 = 400 x 3.14 = 1256 / 2 = 628

628 would be your area if im not mistaken