Ken's POTW


The Difference Pyramid
The University of Central Florida had an excellent Problem of the Week last week. But they don't post solutions. I'd like to accept and post logical solutions to this problem. 

    O
   O O
  O O O
 O O O O
O O O O O
Distribute all the numbers 1 to 15 in the circles so that the number in each circle shows the difference between the two circles on which it sits.

As warm-ups, find solutions for pyramids with 2, 3, or 4 rows.

Source: The UofCF Problem of the Week 2/27/97 The Difference Between Two Circles

Solution
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