The radius of the cone is x = 8 units.
Let's find the value of x.
The volume of a cone of height H and radius R is:
V = (1/3)*π*R²*H
Here we have.
R = x
H =21
V = 448π
Replacing that we get:
448π = (1/3)*π*x²*21
remove pi from both sides:
448 = (1/3)*x²*21
Now solve this for x:
x = √( 3*448/21)
x = 8 units.