Arrange the 28 pieces of a standard domino (0-0 to 6-6) in the board shown, so that equal spot numbers occur in groups of four, forming squares. Fourteen squares should result, each containing four equal spot numbers.

            +---+---+       +---+---+
            |   |   |       |   |   |
            +---+---+---+---+---+---+---+---+
            |   |   |   |   |   |   |   |   |
            +---+---+---+---+---+---+---+---+
            |   |   |   |   |   |   |   |   |
            +---+---+---+---+---+---+---+---+
            |   |   |   |   |   |   |   |   |
            +---+---+---+---+---+---+---+---+
            |   |   |   |   |   |   |   |   |
            +---+---+---+---+---+---+---+---+
            |   |   |   |   |   |   |   |   |
            +---+---+---+---+---+---+---+---+
            |   |   |   |   |   |   |   |   |
            +---+---+---+---+---+---+---+---+
            |   |   |       |   |   |
            +---+---+       +---+---+

I have the same layout as Charlie although my dominoes occupy somewhat different places.  Below this is my layout of the fourteen "quads".

            +---+---+          +---+---+
            |  0     0 |           |  2    2 |
            +---+---+---+---+---+---+---+---+
            |  0  |  0   1  | 1     2 |  2    3 |  3 |
            +    +---+---+---+---+---+---+   +
            |  6  |  6   1  | 1     4 |  4    3 |  3 |
            +---+---+---+---+---+---+---+---+
            |  6  |  6   2  |  2    4 |  4    5 |  5 |
            +    +---+---+---+---+---+---+    +
            |  5  |  5   2  |  2    0 |  0    5 |  5 |
            +---+---+---+---+---+---+---+---+
            |  5  |  5   3  | 3     0 |  0    4 |  4 |
            +    +---+---+---+---+---+---+    +
            |  1  |  1   3  |  3    6 | 6     4 |  4 |
            +---+---+---+---+---+---+---+---+
            |  1    1  |          |  6    6  |
            +---+---+          +---+---+       

This layout maps the fourteen equal four spots numbers in the above layout.  The "doubles" are contained within the bold numbers while the italics signify the outer domino of the group being in a vertical position.

           0      2
              1       3
           6      4
              2       5
           5      0
              3       4
           1      6


                     

Posted by brianjn on 2008-08-15 22:10:32