GWD 5 - 6

sunnylee

Q6:

A certain company assigns employees to offices in such a way that some of the offices can be empty and more than one employee can be assigned to an office. In how many ways can the company assign 3 employees to 2 different offices?

<!--[if !supportLists]-->A. <!--[endif]-->5

<!--[if !supportLists]-->B. <!--[endif]-->6

<!--[if !supportLists]-->C. <!--[endif]-->7

<!--[if !supportLists]-->D. <!--[endif]-->8

<!--[if !supportLists]-->E. <!--[endif]-->9

Answer: D How to use permutation or combination to get the answer?

susanoffice

该题相当于M个东西放在N个盒子中,其通用公式是C(M+N-1,N-1).

susanoffice

刚看了另外一个贴子,看来和M个东西放在N个盒子中还不一样.因为每个employee是不同的.放东西的通用公式认为M个东西是没有区别的.
B  我觉得这题可以这样考虑：

在第一个房间中放的人数可以为：0个、1 个、2个、3个。一旦房间一确定了，房间二就确定了。

所以可能的个数为：

C(3,0) + C(3,1) + C(3,2) + C(3,3) = 8