MathDB
Problems
Contests
National and Regional Contests
USA Contests
USA - Other Middle and High School Contests
Purple Comet Problems
2017 Purple Comet Problems
30
30
Part of
2017 Purple Comet Problems
Problems
(1)
Purple Comet 2017 HS problem 30
Source:
3/19/2020
A container is shaped like a right circular cone with base diameter
18
18
18
and height
12
12
12
. The vertex of the container is pointing down, and the container is open at the top. Four spheres, each with radius
3
3
3
, are placed inside the container as shown. The first sphere sits at the bottom and is tangent to the cone along a circle. The second, third, and fourth spheres are placed so they are each tangent to the cone and tangent to the rst sphere, and the second and fourth spheres are each tangent to the third sphere. The volume of the tetrahedron whose vertices are at the centers of the spheres is
K
K
K
. Find
K
2
K^2
K
2
. https://cdn.artofproblemsolving.com/attachments/9/c/648ec2cf0f0c2f023cd00b1c0595a9396d0ddc.png
geometry
3D geometry