A set of 47 disks are consecutively numbered 1 to 47 and placed in a row as follows: 1, 2, 3, 4, ... 45, 46, 47.

Rearrange the disks so for any two given disks A and B, the disk equal to their arithmetic mean doesn't lie between them. For example, Disk 4 cannot lie between Disk 1 and Disk 7 since the arithmetic mean of 1 and 7 is 4. However, since 7 is not equal to the arithmetic mean of 1 and 4, Disk 7 may lie between Disk 1 and Disk 4.

(In reply to solution (if I understood correctly) by atheron)

First, you seem to have gone farther than you said, as 24 appears twice.

But at the very beginning, 2 appears between 1 and 3, and 25 between 24 and 26, etc., violating the conditions of the puzzle.

Posted by Charlie on 2006-07-05 14:05:43