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A Common Vertex (Posted on 2004-07-12) Difficulty: 2 of 5
Three regular polygons, all with unit sides, share a common vertex and are all coplanar. Each polygon has a different number of sides, and each polygon shares a side with the other two; there are no gaps or overlaps. Find the number of sides for each polygon. There are multiple answers.

  Submitted by Brian Smith    
Rating: 3.0000 (1 votes)
Solution: (Hide)
For the problem as stated, there are six sets of polygons:
3, 7, 42
3, 8, 24
3, 9, 18
3, 10, 15
4, 5, 20
4, 6, 12

If you extend the problem and ask for any number of any polygon at the vertex, the list is as follows:

 3 hexagons;
 2 pentagons; 1 10-gon;
 1 square; 2 8-gons;
 1 square;  1 hexagon; 1 12-gon;
 1 square;  1 pentagon; 1 20-gon;
 4 squares;
 1 triangle; 2 12-gons;
 1 triangle; 1 7-gon; 1 42-gon;
 1 triangle; 1 8-gon; 1 24-gon;
 1 triangle; 1 9-gon; 1 18-gon;
 1 triangle; 1 10-gon; 1 15-gon;
 1 triangle;  2 squares;  1 hexagon;
 2 triangles;  2 hexagons;
 2 triangles;  1 square; 1 12-gon;
 3 triangles;  2 squares;
 4 triangles;  1 hexagon;
 6 triangles;
Charlie produced this result using a program here and a correction here.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
SolutionFormula for the third polygonLarry2018-02-15 09:23:59
shapedavid2004-09-29 14:09:11
Solution"I got six" refinedJerry2004-07-18 09:22:21
SolutionI got sixJerry2004-07-17 17:08:47
re(4): solution- Missed Solution!Charlie2004-07-13 15:37:32
re(3): solution- Missed Solution!SilverKnight2004-07-13 09:26:48
Solutionre(2): solution- Missed Solution!stan2004-07-13 08:51:19
re: charlie's recentrixar2004-07-12 22:31:43
re(3): solutionCharlie2004-07-12 22:06:48
re(2): solutionTristan2004-07-12 20:25:53
correctionrixar2004-07-12 19:32:26
a fewrixar2004-07-12 19:26:03
re: solutionCory Taylor2004-07-12 15:35:41
re(3): solutionCharlie2004-07-12 15:35:21
re(2): solutionThalamus2004-07-12 13:42:53
re: solutionSing4TheDay2004-07-12 13:23:54
re: solutionCharlie2004-07-12 13:16:27
re: solutionSilverKnight2004-07-12 12:21:02
SolutionsolutionThalamus2004-07-12 12:18:48
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