GWD 2-26

fengyun158

Q26:

There are 8 books on a shelf, of which 2 are paperbacks and 6 are hardbacks.  How many possible selections of 4 books from this self include at least one paperback?

 

A.     40

B.     45

C.     50

D.     55

E. 60

答案为c.

但我算出来是d，请教!

C(4,8)-C(4,6)=55

fengyun158

抱歉，答案是D。