N元集合的M元子集元素和被一个整数整除的问题
问题描述:
N元集合的M元子集元素和被一个整数整除的问题
eg:集合{1,2,3,.,51}的5元子集,元素和能被3整除的有________个?
答
1 to 51 can be divided by 3
3,6,9,...,51.
Totally,there are 17 elements
there are:
17C5 = 17.16.15.14.13 / (5.4.3.2.1)
= 6188
5元子集共有=6188个 #