[問題]GWD23 Q 30

[hippo3333]

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: C 50

我的算法 C(2,1) * C (6,3) =40

[chour]

至少一本paperback
一本:C(2,1)*C(6,3)=40
兩本:C(2,2)*C(6,2)=15
40+15=55

[hippo3333]

感謝回答 thanks a lot