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 pagans by a ship sailing the way storm comes up, the extreme of crisis, the leader tell you, as long as half of the ship into the sea, the rest can be spared. We all agree with this approach, and agreements were 30 circle　the number of reported starting from the first person, each number to nine people locked him into the sea, the next and then start from one number off, nine were also into the sea, followed by cycle, until the remaining 15 people so far. The problem is how to row method to put into the sea in all infidels?