HMMT 二月 2008 · GEN2 赛 · 第 3 题
HMMT February 2008 — GEN2 Round — Problem 3
题目详情
- [ 3 ] A 3 × 3 × 3 cube composed of 27 unit cubes rests on a horizontal plane. Determine the number of ways of selecting two distinct unit cubes (order is irrelevant) from a 3 × 3 × 1 block with the property ◦ that the line joining the centers of the two cubes makes a 45 angle with the horizontal plane. 2 2 2 2
解析
- [ 3 ] A 3 × 3 × 3 cube composed of 27 unit cubes rests on a horizontal plane. Determine the number of ways of selecting two distinct unit cubes (order is irrelevant) from a 3 × 3 × 1 block with the property ◦ that the line joining the centers of the two cubes makes a 45 angle with the horizontal plane. Answer: 60 Same as Combinatorics Test problem 1. 2 2 2 2