每30个旅客同乘一条船将全船一半的旅客投入海中，30个人围成一圈，由第一个人数起，依次报数，数到第9人，便把他投入大海中

然后再从他的下一个人数起，数到第9人，再将他扔进大海中。如此循环地进行，直到剩下15个乘客为止。问哪些位置是将是被扔下大海的位置。-Each 30 passenger ride with a boat to ship half of the passengers into the sea, 30 people form a circle, starting　the first person number, followed by newspaper, number of people to the ninth, gave him into the sea

Then　a number of his next play, count to 9 people, and then he was thrown into the sea. So cyclically until the remaining 15 passengers so far. Q. Which position will be dropped sea location.