If r = square root 3V/pi*h , by what number must we multiply V in order to multiply r by 9 ?

Question

a. 3
b. 9/2
c. 9
d. 18
e. 81

please answer and explain

Answer 1

r^2 = k V

k = r^2/V

if you multiply r by 9, then V by 81

k = (9r)^2/81V = r^2/V

so e