100個人做題

來源: 於 2010-06-20 20:08:43 [舊帖] [給我悄悄話] 本文已被閱讀：次

A group of 100 people to answer five questions. 81 got right on first, 91 got right on second, 85 got right on third, 79 got right on fourth, 74 got right on fifth.
Question: At least how many people got at least three questions correct?