[npjlwmqz] Lead or tungsten baseball

density of lead: 11.3 kg/liter density of tungsten: 19.3 kg/liter mass of baseball: 5 to 5.25 oz, according to rules.

[qheanuwc] Ring around the vertex

Position two congruent polyhedra so they touch at a vertex and corresponding edges at the vertices flow as straight lin

[alhgxbnm] Random planar family tree

Simple model: Each generation, one randomly selected male and female produce one random-gender offspring.  Individ

[fspdrsgw] Phase transitions of curves

Given 5 points that determine a conic, fix 4 of them and allow one to move.  Identify the connected region around

[gerfowhn] Disc manifold

First, consider a 2D game character in a square universe.  The character goes out the top of the square and reappe