Question

Find the surface area of sphere whose diameter is 21dm

Answer 1

given diameter[d]=21 cm
so radius[r]=d/2=21/2 cm
Surface area of sphere=4πr²
                                     =4×22/7×21/2×21/2
                                     =66×21
                                     =1386 cm²

Answer 2

surface area of a sphere= 4$\pi$r²
r=21/2
4*22/7*21/2*21/2
=66*21
=1386cm²