Tiling Isosceles Trapezia with Scaled Pentabolo Pairs

Introduction

A pentabolo or pentatan is a plane figure formed by joining five equal isosceles right triangles edge to equal edge. There are 30 different pentaboloes, not counting reflections and rotations.

A scaled pentabolo is a pentabolo whose size may be altered without changing its shape. In geometric terms, it is a family of similar pentaboloes.

A trapezium (trapezoid in Canada and the U.S.) is a plane figure with four sides, two of them parallel. A isosceles trapezium is a trapezium whose two non-parallel sides have the same length.

For every pair of scaled pentaboloes, I show an isosceles trapezium that they can tile, using at least one of each, and using as few tiles as known to be possible. If you find a smaller solution or solve an unsolved case, please write.

Bryce Herdt found improved solutions.

See also

Table of Results

Each figure indicates the number of tiles in the tiling. Pairs not shown in the table cannot tile an isosceles trapezium.

Theoretically, scaled pentabolo 24 and any other scaled pentabolo can together tile an isosceles trapezium. I do not have tilings for all such pairs of scaled pentaboloes.

 123456789101112131415161718192021222324252627282930
2??????54???4??????????26??3??7
8185???36?4?204??4?3???14????79447?
984768574877665685684764643453
24?26523?23??4?2626??4422345663412???6614431233
26??14??6?794?6?4?7??3541?25??66?5???
275372114181143877937732232521254151614355757
3097247?7??3?77??321?6416?22??33??728?

Navigation

Tiles
3 4 5 6 7 8 9 11 12
14 15 16 18 20 21 22 23 24
25 26 28 32 33 34 35 36 37
41 42 43 45 52 64 66 79

3 Tiles

4 Tiles

5 Tiles

6 Tiles

7 Tiles

8 Tiles

9 Tiles

11 Tiles

12 Tiles

14 Tiles

15 Tiles

16 Tiles

18 Tiles

20 Tiles

21 Tiles

22 Tiles

23 Tiles

24 Tiles

25 Tiles

26 Tiles

28 Tiles

32 Tiles

33 Tiles

34 Tiles

35 Tiles

36 Tiles

37 Tiles

41 Tiles

42 Tiles

43 Tiles

45 Tiles

52 Tiles

64 Tiles

66 Tiles

79 Tiles

Last revised 2025-10-13.


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Col. George Sicherman [ HOME | MAIL ]