请大家帮我看看这道题

yunfei306

Of the science books in a certain supply room, 50 are on botany, 65 are on zoology, 90 are on physics, 50 are on geology, and 110 are on chemistry. If science books are removed randomly from the supply room, how many must be removed to ensure that 80 of the books removed are on the same science?

 

A.81

B.159

C.166

D285

E.324

为什么正确答案是E？

irvah

我的理解：求要能保证这些被移动过的书里有80本是on the same science的移动次数。

80本on the same science 只可能是physics or chemistry。要ensure，就是说取到那个次数的时候，一定有80本是on the same science。

50botany + 65zoology + 50geology + 79 physics or chemistry + 80 chemistry or physics = 324

不知道对是否lz有帮助