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BP323 Jigsaw puzzle pieces can be assembled into a square vs. jigsaw puzzle pieces cannot be assembled into a square.
(edit; present; nest [left/right]; search; history)
COMMENTS

Although it takes time to check each individual example, the right answer is likely the first thing a person would think of upon seeing this.

CROSSREFS

Adjacent-numbered pages:
BP318 BP319 BP320 BP321 BP322  *  BP324 BP325 BP326 BP327 BP328

KEYWORD

notso, hardsort, traditional

CONCEPT jigsaw_puzzle (info | search),
tiling (info | search),
imagined_motion (info | search),
motion (info | search)

AUTHOR

Aaron David Fairbanks

BP335 Tessellates the plane vs. does not tessellate the plane.
(edit; present; nest [left/right]; search; history)
COMMENTS

EX7152 is an example of a shape than can be stretched in such a way that it no longer tessellates the plane. This is a property that is only exhibited by shapes that tessellate with rotated copies of themselves. - Leo Crabbe, Mar 05 2021

CROSSREFS

Adjacent-numbered pages:
BP330 BP331 BP332 BP333 BP334  *  BP336 BP337 BP338 BP339 BP340

KEYWORD

nice, stretch, unstable, math, hardsort, creativeexamples, proofsrequired, perfect, pixelperfect, traditional

CONCEPT infinite_plane (info | search),
tessellation (info | search),
tiling (info | search)

WORLD

shape [smaller | same | bigger]
zoom in left (fill_shape)

AUTHOR

Aaron David Fairbanks

BP344 Shape can tile itself vs. shape cannot tile itself.
(edit; present; nest [left/right]; search; history)
COMMENTS

Left examples are sometimes called "rep-tiles."


The tiles all must be the same size. More specifically, all left examples can tile themselves only using scaled down and rotated versions of themselves with all tiles the same size. Right examples cannot tile themselves using scaled down rotated versions of themselves or even reflected versions of themselves with all tiles the same size.


Without the puzzle piece-like shape EX4120 on the right side the current examples also allow the solution "shape can tile with itself so as to create a parallelogram vs. shape cannot tile with itself so as to create a parallelogram."

CROSSREFS

See BP532 for a version with fractals.

Adjacent-numbered pages:
BP339 BP340 BP341 BP342 BP343  *  BP345 BP346 BP347 BP348 BP349

EXAMPLE

Go to https://oebp.org/files/yet.png for an illustration of how some left-sorted shapes tile themselves.

KEYWORD

hard, nice, precise, notso, unstable, math, hardsort, creativeexamples, proofsrequired, perfect, traditional

CONCEPT recursion (info | search),
self-reference (info | search),
tiling (info | search),
imagined_shape (info | search),
imagined_entity (info | search)

WORLD

shape [smaller | same | bigger]

AUTHOR

Aaron David Fairbanks

BP532 Self-tiling fractal using one size of tile vs. does not tile itself with a single size of itself.
(edit; present; nest [left/right]; search; history)
CROSSREFS

This is BP344 ("rep-tiles") but for fractals.

See BP1119 for the version with multiple different sizes of tile allowed.

Adjacent-numbered pages:
BP527 BP528 BP529 BP530 BP531  *  BP533 BP534 BP535 BP536 BP537

KEYWORD

hardsort, proofsrequired, perfect, infinitedetail, contributepairs

CONCEPT fractal (info | search),
recursion (info | search),
self-reference (info | search),
tiling (info | search)

WORLD

[smaller | same | bigger]
zoom in left (fractal_self_tile)

AUTHOR

Aaron David Fairbanks

BP853 Prime knot vs. composite knot.
(edit; present; nest [left/right]; search; history)
REFERENCE

https://en.wikipedia.org/wiki/Prime_knot

CROSSREFS

Adjacent-numbered pages:
BP848 BP849 BP850 BP851 BP852  *  BP854 BP855 BP856 BP857 BP858

KEYWORD

math, hardsort

CONCEPT knot (info | search)

WORLD

knot [smaller | same | bigger]

AUTHOR

Aaron David Fairbanks

BP860 Finitely many copies of the shape can be arranged such that they are locked together vs. not so.
(edit; present; nest [left/right]; search; history)
CROSSREFS

This is a generalisation of BP861.

Adjacent-numbered pages:
BP855 BP856 BP857 BP858 BP859  *  BP861 BP862 BP863 BP864 BP865

KEYWORD

hard, nice, stub, precise, stretch, unstable, hardsort, challenge, creativeexamples, perfect, pixelperfect

CONCEPT tiling (info | search)

WORLD

fill_shape [smaller | same | bigger]

AUTHOR

Leo Crabbe

BP863 Two shapes can tessellate the plane together vs. not so.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP858 BP859 BP860 BP861 BP862  *  BP864 BP865 BP866 BP867 BP868

KEYWORD

nice, precise, allsorted, math, hardsort, creativeexamples, unorderedpair

CONCEPT infinite_plane (info | search),
tessellation (info | search),
tiling (info | search)

WORLD

2_shapes [smaller | same | bigger]

AUTHOR

Leo Crabbe

BP1005 The collection of dot clumps has the same numerical property as each of the dot clumps vs. not so.
(edit; present; nest [left/right]; search; history)
CROSSREFS

This is a version of BP999 with only numbers.

Contrast BP1006, which is very similar.

Adjacent-numbered pages:
BP1000 BP1001 BP1002 BP1003 BP1004  *  BP1006 BP1007 BP1008 BP1009 BP1010

KEYWORD

nice, notso, hardsort, left-narrow, rules

CONCEPT recursion (info | search),
self-reference (info | search)

WORLD

[smaller | same | bigger]
zoom in left | zoom in right

AUTHOR

Aaron David Fairbanks

BP1006 The sum of all dot clumps has the same numerical property as each of the dot clumps vs. not so.
(edit; present; nest [left/right]; search; history)
CROSSREFS

This is a version of BP1003 with only numbers.

Contrast BP1005, which is very similar.

Adjacent-numbered pages:
BP1001 BP1002 BP1003 BP1004 BP1005  *  BP1007 BP1008 BP1009 BP1010 BP1011

KEYWORD

nice, hardsort, left-narrow, rules

CONCEPT recursion (info | search),
self-reference (info | search)

WORLD

[smaller | same | bigger]
zoom in left | zoom in right

AUTHOR

Leo Crabbe, Aaron David Fairbanks

BP1119 Tiled by finitely many smaller copies of itself (different sizes allowed) vs. not so.
(edit; present; nest [left/right]; search; history)
COMMENTS

These are sometimes called "irreptiles".

CROSSREFS

See BP532 for the version with only one size of tile allowed.

Adjacent-numbered pages:
BP1114 BP1115 BP1116 BP1117 BP1118  *  BP1120 BP1121 BP1122 BP1123 BP1124

KEYWORD

hardsort, proofsrequired, perfect, infinitedetail

CONCEPT fractal (info | search),
recursion (info | search),
self-reference (info | search),
tiling (info | search)

WORLD

[smaller | same | bigger]

AUTHOR

Aaron David Fairbanks

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