we know that
volume of a hemisphere=(1/2)*(4/3)*pi*r³----> (2/3)*pi*r³
volume of a cone=(1/3)*pi*r²*h
h=r
so
volume of a cone=(1/3)*pi*r²*r----> (1/3)*pi*r³
volume of a hemisphere/volume of a cone
= [(2/3)*pi*r³]/[(1/3)*pi*r³]
=(2/3)/(1/3)
=2
volume of a hemisphere=2*volume of a cone
the volume of the hemisphere is twice the volume of the cone