Consider all nine-digit numbers consisting of one each of the digits 1 through 9.

What is the sum of these numbers?

0 (Zero).  For every positive nine-digit number there is a negative nine-digit number.

123456789 + -123456789 = 0
123456798 + -123456798 = 0
123456879 + -123456879 = 0
....
987654521 + -987654321 = 0

Of course, considering only positive integers, the solution given by tomarken,  201599999798400, is correct. 

Edited on April 15, 2006, 7:22 am

Posted by Dej Mar on 2006-04-15 06:14:30