Tuesday, 9 June 2015

mathematics - A 3x3 grid of numbers with unique row and column ranges



Can you place every number from 1 to 9 into a 3x3 grid such that the range of every row and column is a unique value? The range of a row is the difference between its maximum and minimum values (similarly for columns).


Good luck!



Answer



Here is one solution:



 1 3 9   8
5 7 6 2
4 8 2 6

4 5 7


I solved it by



first placing the 1 and 9 in one row, to get the largest range. The next numbers I placed were 2, 8, 3, 7, 4, 6, 5. In other words I worked from the outside (largest/smallest) inwards. Each time I tried to place the number such that a new row/column would provide the next missing range or do nothing.



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