15题:如果按照4*3算的话,得到的其实是排序
如果按照题目说的只是4种水果取两种的话,应该是4个里面任选俩,C 2 4 = 6 吧
Reference:Prep 8 - 1
If a committee of 3 people is to be selected from among 5 married couples so that the committee does not include two people who are married to each other, how many such committees are possible?
Answer: 80 = 2^3 * C3 5 = 8*10