The volume of the cone is calculated by the formula:
V = B*H/3
r=D/2 = 6/3 = 2
where B is surface area of basis and H is height.
B is circle which fomula for surface is:
B = r^2 * pi = 3^2*3,14 = 9*3,14 = 28.26
from condition of height we write:
H = 3*D = 3*6 = 18
now volume is:
If we express all of that in equation of volume we get:
V = 1/3* 3^2*3,14*18
