HMMT 十一月 2014 · 团队赛 · 第 4 题

英文解析

4. [ 3 ] How many ways are there to color the vertices of a triangle red, green, blue, or yellow such that no two vertices have the same color? Rotations and reflections are considered distinct.
   Answer: 24 There are 4 ways to color the first vertex, then 3 ways to color the second vertex tobe distinct from the first, and finally 2 ways to color the third vertex to be distinct from the earliertwo vertices. Multiplying gives 24 ways.