we know that
[volume of a original cone]=(1/3)*pi*r²*h
[volume of a dilated cone]=(1/3)*pi*(r/2)²*(h/2)--->(1/8)* [(1/3)*pi*r²*h]
so
[volume of a dilated cone]=(1/8)* [volume of a original cone]
the answer is
the volume of the cone will be reduced one eighth