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BP816 Cross section of a cylinder vs. not cross section of a cylinder
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP811 BP812 BP813 BP814 BP815  *  BP817 BP818 BP819 BP820 BP821

KEYWORD

precise, notso, stretch, unstable, perfect

CONCEPT cross_section (info | search)

WORLD

fill_shapes [smaller | same | bigger]

AUTHOR

Leo Crabbe

BP818 Dot's position within square is center of square's position within panel vs. not so.
(edit; present; nest [left/right]; search; history)
COMMENTS

All examples in this problem are dots inside square outlines.

CROSSREFS

Similar to BP1122 (the "fractal" version).

Adjacent-numbered pages:
BP813 BP814 BP815 BP816 BP817  *  BP819 BP820 BP821 BP822 BP823

KEYWORD

nice, notso, boundingbox, absoluteposition

CONCEPT bounding_box (info | search),
self-reference (info | search),
center (info | search),
distance_from_center (info | search)

WORLD

point_inside_square [smaller | same | bigger]

AUTHOR

Leo Crabbe

BP823 Conic section (plot of solution to conic equation) vs. not so.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP818 BP819 BP820 BP821 BP822  *  BP824 BP825 BP826 BP827 BP828

KEYWORD

notso, math, left-couldbe

AUTHOR

Aaron David Fairbanks

BP825 Ticks mark an infinite sequence of angles on circle such that each angle is the double of the subsequent angle in the sequence (angle measured from rightmost indicated point) vs. not so.
(edit; present; nest [left/right]; search; history)
COMMENTS

This is solvable; it was solved by Sridhar Ramesh.


A full turn is considered "the same angle" as no turns; likewise for adding and subtracting full turns from any angle. All sequences of angles shown start at the rightmost tick.


It doesn't matter whether the angle is measured clockwise or counterclockwise, as long as the choice is consistent.

CROSSREFS

Adjacent-numbered pages:
BP820 BP821 BP822 BP823 BP824  *  BP826 BP827 BP828 BP829 BP830

KEYWORD

hard, convoluted, notso, math, solved

CONCEPT sequence (info | search)

AUTHOR

Aaron David Fairbanks

BP852 Object shown below is the "limit" of the sequence above (end result after "infinite time") versus not so.
(edit; present; nest [left/right]; search; history)
COMMENTS

The conceptual limit of the sequence may not be the limit of the points in the image. For example in a sequence of halvings the limit value is never reached, so the bottom would never change color and thus its limit would not would not either.


Sequences progress from left to right (and there is not usually a way to intuitively extend the sequence in the other direction).

CROSSREFS

Adjacent-numbered pages:
BP847 BP848 BP849 BP850 BP851  *  BP853 BP854 BP855 BP856 BP857

KEYWORD

notso, creativeexamples, perfect, infinitedetail, assumesfamiliarity, structure, contributepairs, rules

AUTHOR

Aaron David Fairbanks

BP897 Wide angles connected to narrow angles vs. not so.
(edit; present; nest [left/right]; search; history)
COMMENTS

Another solution is that right examples can be folded down flat onto one isosceles triangle while left examples cannot.

All examples in this Problem feature four isosceles triangles connected by corners and/or edges.

CROSSREFS

This was conceived as a false solution for BP898.

Adjacent-numbered pages:
BP892 BP893 BP894 BP895 BP896  *  BP898 BP899 BP900 BP901 BP902

KEYWORD

precise, allsorted, notso, traditional, preciseworld

CONCEPT triangle (info | search)

WORLD

[smaller | same | bigger]

AUTHOR

Molly C Klenzak, Aaron David Fairbanks

BP898 Can fold into tetragonal disphenoid ("isosceles tetrahedron") vs. cannot.
(edit; present; nest [left/right]; search; history)
COMMENTS

Which two sides are the long sides and which side is the short side, or equivalently which angles are the wider angles and which angle is the narrower angle, is the only relevant information to consider for each triangle. Triangles are all assumed isosceles and congruent to one another.


All examples in this Problem feature four of these triangles connected by corners and/or edges.

CROSSREFS

BP897 was conceived as a false solution for this.

Adjacent-numbered pages:
BP893 BP894 BP895 BP896 BP897  *  BP899 BP900 BP901 BP902 BP903

KEYWORD

hard, precise, allsorted, notso, math, preciseworld

CONCEPT triangle (info | search)

WORLD

[smaller | same | bigger]

AUTHOR

Molly C Klenzak

BP905 Graph can be redrawn such that no edges intersect vs. not so.
(edit; present; nest [left/right]; search; history)
COMMENTS

A graph is a collection of vertices and edges. Vertices are the dots and edges are the lines that connect the dots. On the left, all edges can be redrawn (curved lines are allowed and moving vertices is allowed) such that no edges cross each other and each vertex is still connected to the same other vertices. These graphs are called planar.

CROSSREFS

Adjacent-numbered pages:
BP900 BP901 BP902 BP903 BP904  *  BP906 BP907 BP908 BP909 BP910

KEYWORD

nice, precise, allsorted, notso, math, left-null, preciseworld

CONCEPT graph (info | search),
topological_transformation (info | search)

WORLD

connected_graph [smaller | same | bigger]

AUTHOR

Molly C Klenzak

BP915 Finite number of dots vs. infinite number of dots.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP910 BP911 BP912 BP913 BP914  *  BP916 BP917 BP918 BP919 BP920

KEYWORD

less, notso, spectrum, number, example, left-null, impossible, experimental

CONCEPT finite_infinite (info | search)

WORLD

dots [smaller | same | bigger]

AUTHOR

Jago Collins

BP946 Can be constructed using 2 identical copies of an image (full overlapping not allowed) vs. not so.
(edit; present; nest [left/right]; search; history)
COMMENTS

"Full overlapping not allowed" means you cannot overlay an image onto itself without moving it; if this were allowed all images would be sorted on the left. The copies can be moved around (translated) in 2D but can not be flipped or rotated.


There are examples on the right drawn with thick lines, and these could be created by copying an image with slightly thinner lines and moving it over a tiny amount. If you fix this issue by saying "the copy has to be moved over more than a tiny amount" then the Bongard Problem is perfect but not precise, but if you fix this issue by saying "interpret the figures as made up of (infinitesimally) thin lines" then it's precise but not perfect. - Aaron David Fairbanks, Jun 17 2023

CROSSREFS

Adjacent-numbered pages:
BP941 BP942 BP943 BP944 BP945  *  BP947 BP948 BP949 BP950 BP951

KEYWORD

nice, notso, creativeexamples

AUTHOR

Leo Crabbe

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