Answer:
Explanation:
The volume of a cone is

Filling in what we have:
and simplifying a bit:

Multiply both sides by 3 to get:

Divide both sides by 12.56 to get:
and take the square root of both sides to find the radius:
r = 5
If the radius is 5 and the radius by definition is half the diameter, then the diameter is 10 inches.