15名基督教徒和15名异教徒同乘一船航行，途中风浪大作，危机万分，领航者告诉大家，只要将全船的一半人投入海中，其余人就能幸免。大家都同意这个办法，并协定者30人围成一圈；由第一个人起报数，每数至第9人便把他投入海中，下一个接着从1开始报数，第9人又被投入海中，依次循环，直至剩下15人为止。问题是如何排法使投入海中的人全为异教徒？-15 Christians and 15 infidels passengers a ship sailed the way storms masterpiece, extreme crisis, the leader told everyone, as long as the half of the ship into the sea, the rest of the people will be able to be spared. Everyone agrees with this approach, and 30 of the Agreement by a circle　reported number from the first person, every few 9 put him into the sea, next followed from 1 Countin 9th and into the sea, followed by cycle, until the rest of the 15 people so far. The problem is how to row into the sea by all infidels?