请教数学题目！

pyrbbb

请教一道数学题目：

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?

answer: 324

请问为啥是：50+65+50+79+79？谢谢指教！

pyrbbb

谢谢啦：）

mingzhu

应该是50+65+50+80+79=324

carollai

为确保拿走的书中有80本属同一学科，要按照最霉的方法算：先拿了50本b,再拿了65本z，接着拿50本g，拿79本p(或c),然后拿79本c(或p),最后随便再拿一本（p或c）就可以保证有80本同样了。答案是：50+65+50+79+79+1=324