Ivo Beckers
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Simple geometry. Or is it?
78 votes

I know the answer is already given but I'd like to show an easy explanation of why the 2 planes are coplanar. Take this image: Consider two pyramids sitting side by side, and draw a line between ...

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Professor Halfbrain and the fantasy knight
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27 votes

Yes there is a solution with a very simple strategy: Start in (1,1). Always go the right most square that's unvisited I'll try to illustrate it. I checked it by hand on an 9x9 board and a very nice ...

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7# Emertxe Gnidocne
27 votes

I'm stuck at the moment but this is what I got so far: Rotating and flipping all texts correctly should give: Encoding Extreme #7 I think the time has came. I need you to help me This is going ...

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Who killed Professor Cal?
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23 votes

It's Because

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Points on the boundary of a circle
21 votes

They do exist. And they are actually called Brahmagupta Hexagons. An example is this: Which I took from this paper which has a lot more info on them

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Rubik's cube 19 move Solution
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21 votes

Given any position you know that has 20 moves (like the Superflip) just do one move towards the solution and you have a position that requires 19 moves.

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Which computer-made song is this?
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19 votes

The song is clearly supposed to be Which is a well known song by With some imagination it is pronounced the same as

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Heaps of marbles
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18 votes

This is how:

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The Challenge Square
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17 votes

You can do it like this: The cut starts right in the center of those sides.

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What has been added?
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16 votes

By using the compare tool Beyond Compare this appeared: So she is hiding

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The adventitious 18-gon
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15 votes

To illustrate the puzzle I made the following image: All angles I entered can be simply calculated using the fact any n-gon has a total of $180 + (n-3) \cdot 180 °$. Now let's call the intersection ...

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The Price is Right
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15 votes

If I'm not mistaken $P(\text{to win car}) = 1 - P(\text{only draw Cs}) - P(\text{only draw As}) - P(\text{only draw Rs}) - P(\text{only draw Cs or As}) - P(\text{only draw Cs or Rs}) - P(\text{only ...

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Professor Halfbrain and the tilted cube
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15 votes

Such a cube The first thing I noticed that this essential the same question as Can you rotate a unit cube in such a way that the height to the table of the corners form an arithmetic sequence for ...

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A simple visual puzzle to die for
14 votes

It will look like this: Because in a single row you overlap the first two images and the third is the result of that, with double lines being removed.

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Find the next term in the number series?
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14 votes

It seems to be x3, +4, x5, +6, x7, +8 and so on

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Clear board in Othello
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13 votes

Yes, I found this video on YouTube that has this "perfect game". Terrible music by the way https://www.youtube.com/watch?v=prWG1OFgVqg

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Spiders on a cube
12 votes

Not a definite answer but I narrowed it down to 2 possibilities. It's either In this case or the second possible answer is Because

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The game with cookies on a red and a blue plate
11 votes

How:

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Touching Matchsticks
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11 votes

I must admit that I found It with google but this is the solution:

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And the average is 51.5625
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10 votes

Note: 51.5625 = 825/16 To calculate the sum for a given $n$ we can do $\frac{n \cdot (n+1)}{2}$. Then we need to have that $\frac{n \cdot (n+1)}{2} - \frac{825 \cdot (n - 4)}{16}$ is a number that can ...

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Mutilated chessboard
10 votes

First assume that this is possible. Look at the first row. It has 2014 available spaces. This means that there are at least 2014 % 4 = 2 pieces that are 1x4. The second row now has 2015 - 2 = 2013 ...

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Placing seven point-sized pawns
10 votes

Not really an answer but I'd like to add my thought process to this

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Help with the name of this puzzle
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10 votes

That specific one looks like a Varikon tower to me. See http://www.cs.brandeis.edu/~storer/JimPuzzles/MANIP/VarikonTowers/VarikonTowers.pdf http://www.jaapsch.net/puzzles/tower.htm

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The final showdown
10 votes

The solution is: ┌────────────────────────┐ │ O ~ ~ ~ Λ ~ < > │ 4 │ ~ ~ Λ ~ x ~ ~ ~ │ 2 │ O ~ x ~ x ~ < > │ 5 │ ~ ~ V ~ V ~ ~ ~ │ 2 │ ~ ~ ~ ~ ~ ~ ~ Λ │ ...

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The Origins of a Confusing Maze
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10 votes

I think the below picture is your intended solution where red dots are where the fuses are lit and black where they die out. however, the error is on the pink dot because at that point 2 sparks need ...

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A chess board and a coin!
9 votes

I'm not 100% percent sure but I think it's the following

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A party puzzler
9 votes

As pointed out by ghost_in_the_code is a solution, however he doesn't state why it's the only solution. To show it is the only solution we have to realize that what is asked is how many vertices are ...

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A tiny question: The little big family
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9 votes

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Dragon lizards in Hogwarts
9 votes

Although mfc32 answer is correct I'd like to add a more mathematical approach:

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Introducing Domidoku!
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8 votes

I worked with @Techidiot's sudoku solution and solved the Dominosa: The key to understand is that unlike regular Dominosa there are no tiles with same digits. and the grey cells indicate cells that ...

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