MathDB
Chess board

Source: Cono Sur 1993-problem 4

May 30, 2006
combinatorics unsolvedcombinatorics

Problem Statement

On a chess board (8āˆ—88*8) there are written the numbers 11 to 6464: on the first line, from left to right, there are the numbers 1,2,3,...,81, 2, 3, ... , 8; on the second line, from left to right, there are the numbers 9,10,11,...,169, 10, 11, ... , 16;etc. The \"+\" and \"-\" signs are put to each number such that, in each line and in each column, there are 44 \"+\" signs and 44 \"-\" signs. Then, the 6464 numbers are added. Find all the possible values of this sum.
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