2008年全国初中数学竞赛四川赛区初赛试题及参考答案.doc

文档介绍：五、(本大题满分25分)如图,将3枚相同硬币依次放入一个4×4的正方形格子中(每个正方形格子只能放1枚硬币).求所放的3枚硬币中,、(本大题25分)解:1、计算总的放法数N:第一枚硬币放入16个格子有16种放法;第二枚硬币放入剩下的15个格子有15种放法;,总的放法数N=16×15×14=3360.·············································10分2、计算满足题目要求的放法数m:第一枚硬币放入16个格子有16种放法,,,,满足题目要求的放法数m=16×9×4=576.···································20分所求概率P=3561415164916??????Nm.···················································25分