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Fill in the empty squares with As, Bs, Cs, Ds and Es so that no horizontal, vertical or diagonal line contains a letter more than once (including diagonals like the one A and E are on). Which letter goes in the square marked *?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
This problem is taken from the UKMT Mathematical Challenges.View the previous week's solution