All Questions
Tagged with topology logical-deduction
6
questions
3
votes
3
answers
630
views
rope - knotted or does not knot [closed]
The figure shows the shadow of a piece of rope on the ground, and you can't see which part is on which part; Suppose the rope is placed completely randomly. Now tighten the two ends of the rope to the ...
- 101
-2
votes
2
answers
322
views
Are three colors sufficient to color a map with convex regions?
The four color theorem states that no more than four colors are required to color the regions
of any map so that no two adjacent regions have the same color.
If all regions are convex (i.e. the region ...
- 12.3k
7
votes
1
answer
319
views
wandering knight
Suppose a land with a finite number of castles. Each castle is connected (via roads) with exactly 3 other castles.
One knight leaves from his castle and starts travelling. He moves in the following ...
11
votes
3
answers
20k
views
Connect the colored dots
I've got this:
By connecting the dots, I get this:
Could you do the same for this one:
There is a unique solution.
The rules are: You have to use every square, lines can't cross each other and you ...
- 255
14
votes
1
answer
1k
views
Ernie and the Underground Network
I haven't seen Ernie for a few weeks - he's been on holiday in the People's Republic of Kzijekistan (PRK). But yesterday I got an e-mail and thought I would share it with you. It reads as follows:
...
- 14k
27
votes
5
answers
11k
views
Is there a proof that a map of the United States requires 4 colors?
The Four color theorem states that no more than four colors are required for any map. Can it be proved or disproved that 3 colors can be used for United States map?
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