Fill in each location with a number from 1-15 such that each number is the difference between the two locations immediately below it. Each number should be used only once.

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There are only 5 numbers to choose from which are all placed in the bottom row. The remaining pyramid entries are dependent on these five numbers. It is easy to see that these numbers must include 15, 14 and 13, and the three cannot all be adjacent. Using this information, a program can systematically determine the proper results.

There are two solutions, which are symmetric. Hence there is really only one, and it goes like this:

           5

        4    9

      7   11    2

   8    1    12   10

6    14  15    3     13

Posted by Eric on 2004-07-13 10:15:27