10 is diameter, we first find the radius which is 10/2 = 5 and so we know the area formula of the circle is πr^2 so 5^2 is 25 and then there's a π at the end so 25π, but it's a semicircle so 25π/2 which is 12.5π, if it's in base 10 (decimal form) then simply do 12.5 x 3.14 = 39.25
