22

You have three flat pieces, as shown:

enter image description here

Arrange them flat, without overlap, such that the shape formed by the black parts is congruent to the shape formed by the white parts. Rotation and reflection are allowed.

Find at least 77777 distinct solutions.

If you find a single one, feel free to post a partial.

Quick note to clarify the aim of this puzzle: This is not a trick question where you need to stack the shapes/make a 3d shape etc. It's exactly what it appears to be. The solutions are just really hard to find.

TheGreatEscaper
  • 11,946
  • 1
  • 42
  • 96

3 Answers3

27

Here are 6 solutions, with instructions for another 77,771. The seed solution’s shape came from seeking threefold angular symmetry, for rotational simplicity, with the hope that one solution can become 77,777 merely by stretching such a configuration.   (Good news, stretching worked as hoped.)

Note that solutions 4− 6 are similar to solutions 1− 3, as if the pieces had passed through the center. Thanks to elias’s insight that one solution can become another by rotating the pieces by equal amounts, solutions 4− 6 can also be derived from solutions 1− 3 by turning each piece 180° locally before turning the entire plane 180°.

The seed solution’s details came from discovering that the pieces could be repeated to produce equal black and white patterns shifted relative to each other.

The pieces might as well have their own coordinate-system grids, at 120° angles to each other.   For any of 77,771 further solutions, just select virtually any coordinate pair and orientation and place each piece on its own grid, at those coordinates and with that orientation.   Here is a picture of those grids, with a solution for coordinates (-3­.­5, 4) and orientation 90° counter-clockwise and flipped.

Here are those pieces and their grids individually and compared to their seed positions /orientations.

These coordinate grids could also be extended out of the plane (violating the puzzle statement) to produce congruent 3-dimensional color patterns. That is, each piece could also be tilted and lifted out of the plane by a common arbitrary altitudinal angle and arbitrary offset along with elias’s arbitrary azimuthal angle.

humn
  • 21,899
  • 4
  • 60
  • 161
  • Nicely solved! $ $ – Deusovi Feb 13 '17 at 00:13
  • Great job! Essentially all the solution variations are based on this same concept. – TheGreatEscaper Feb 13 '17 at 00:35
  • And you can be sure, @TheGreatEscaper, that the better picture(s) is (are) taking so long because it (they) include the negative case of this seed – humn Feb 13 '17 at 00:37
  • There's not just a negative case... you can characterise all infinite families in a simple way! – TheGreatEscaper Feb 13 '17 at 00:49
  • @Humn no worries :) it's always my pleasure to see you enjoying my more mathy puzzles! – TheGreatEscaper Feb 13 '17 at 00:50
  • All righty, @TheGreatEscaper, this is as general as I could think of with the same seed. Please give me another hint if you were alluding to something more. – humn Feb 13 '17 at 05:53
  • 2
    I think each piece can be rotated with the same - but arbitrary - $\varphi$ angle around its corresponding axis (marked by black dots on your drawings). – elias Feb 13 '17 at 06:30
  • Good one, @elias! Suddenly I think so too. And suspect that the angle could be 3-dimensional. Your generalization has been edited and credited in the solution. – humn Feb 13 '17 at 07:03
  • Thanks for the credits, @humn. I think this is the first time I've seen my name in the same sentence with the word 'azimuthal'. Probably the very first time I've seen that word at all. – elias Feb 13 '17 at 07:07
  • Thanks again for the generalization, @elias. So I borrowed the idea from you and the term from astronomy. – humn Feb 13 '17 at 07:11
  • Cool! I'm going to post my own solution (leaving yours as the accepted, of course) which will explain the even more general solution! Edit: perhaps 'even more general' isn't quite the right term, but 'even easier to express' is a better way to put it. – TheGreatEscaper Feb 13 '17 at 08:35
  • I didn't quite understand your explanation of coordinates, but couldn't an infinity of solutions be found by taking any of the 6 bases and moving the pieces further away from the center? – Weckar E. Feb 13 '17 at 14:29
  • You're right, @Weckar E, moving the pieces further out is how the solution originally developed. I'm working on a clearer explanation. – humn Feb 13 '17 at 14:48
16

How to make a solution in 3 easy steps! An illustrated guide to Congruence Infinity:

  1. Drop a P pentomino (reflections allowed) somewhere on a plane, and also put a point somewhere (not too close to the P pentomino, please!)

enter image description here

  1. Clone the P pentomino at 120 and 240 degrees rotated around the point

enter image description here

  1. Place the three pieces on the three P pentominoes as follows (in any order):

enter image description here

Voila!

TheGreatEscaper
  • 11,946
  • 1
  • 42
  • 96
  • Good for giving away your secrets! This is such a neat little set of pieces that pack into a couple of surprisingly difficult puzzles. I suspect some fun test-solving along the way. – humn Feb 13 '17 at 13:13
4

Keeping the conditions in mind I came up with the following solution.

One of the solution could be as follows: