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MathNet 2011 Question 11

Math Olympiad Vault · MathNet 2011

Question 11

Emerald writes the integers from $1$ to $9$ in a $3 \times 3$ table, one number in each cell, each number appearing exactly once. Then she computes eight sums: the sums of three numbers on each row, the sums of the three numbers on each column and the sums of the three numbers on both diagonals.

a. Show a table such that exactly three of the eight sums are multiples of $3$.

b. Is it possible that none of the eight sums is a multiple of $3$?