Question

find the area of semicircle diameter 21cm using formula

Answer 1

radius =d/2=21/2=10.5cm
Area of semi circle =1/2*22/7*(10.5*10.5)
Area of semi circle =11/7*110.25
Area of semi circle =11*15.75
Area of semi circle=173.25cm2

Answer 2

Hello..
Area of Semi-circle  = (1/2) Π r²

  Here r= 21/2cm and Π = 22/7 

           = (1/2) x (22/7) x (21/2)^2

           = (1/2) x (22/7) x 21/2×21/2

           = 1 1×3×21/4
= 33×21/4
= 693/4
           = 173.25 cm²
hopes it will help u
thanks