Posted by danielle on .
One right circular cone is set inside a larger circular cone. The cones share the same Axis, the same vertex, and the same height. Find the volume of the space between the cones of the diameter of the inside cone is 6in., the diameter of the outside cone is 9in and the height of both is 5 in. Round to the nearest tenth.

Geometry 
danielle,
The surface area of a cone is 16.8pi in squared. The radius 3 in. What is the slant height?

Geometry 
Steve,
for the volumes, just subtract the smaller from the larger:
π/3 (81)(5) = π/3 (36)(5) = 75π
area = πr(r+s)
16.8π = π(3)(3+s)
5.6=3+s
s=2.6
s cannot be less than r.
Evidently you do not want to include the base of the cone, so
16.8π = πrs
16.8π = 3πs
s = 5.6