just plugin values to make easy

if r=1
then V = 1/(2x1)^3 = 1/2^3 = 1/8

r= 1/2 given

V = 1/(2 x 1/2)^3 = 1/1^3 = 1/1 = 1

Thus V is multiplied by 8: 1/8 x 8 = 1

B

(or)

V=1/(2r)^3=1/8*r^3

r=r/2

then

V=1/r^3

in order to get V original value V must be multiplied by 8


ie
8V=1/r^3

V=1/8*r^3 (Original value)

So, is the question really asking, what does r need to be mutiplied by to retain the orignial value when r is halved??? Thanks for your help!