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Different Magic Square

Stage: 3 Short Challenge Level: Challenge Level:1

The numbers $13$, $10$ and $7$ form a diagonal, so this tells you the total of each row, column and diagonal is $13+10+7=30$. The first column then has middle cell $30 - 13 - 9 = 8$, the bottom row has middle cell $30 - 9 - 7 = 14$ and the other diagonal has top-right cell $30 - 9 - 10 = 11$.

The other two cells can then be calculated in the same way, giving the completed grid as below:


This problem is taken from the UKMT Mathematical Challenges.