Rob Watts
  • Member for 7 years, 6 months
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Unexpected hanging paradox
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30 votes

The biggest problem with the prisoner's proof is that his model is incomplete. One piece of that is that it merges two key variables - days on which the execution can happen, and days on which the ...

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Fisherman boat and sea level
29 votes

Assuming that the anchor will actually sink and reach the bottom of the very small lake, the water level of the lake will Reason: More intuitive reasoning:

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Protagoras's Paradox. An Unsolved Court Case
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22 votes

There is no paradox. The teacher should get paid, one way or another. The key to understanding the situation is realizing there are multiple slightly different scenarios that are all being described ...

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The treasure hunt
20 votes

He should open the Explanation of the logic (assumes the inscriptions are intended to be helpful): I'm also assuming here that the dragon referred to by the silver chest's inscription is the same ...

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Why does the 4x4 Rubik's cube have parity cases, while the 3x3 does not?
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15 votes

The easiest explanation would be that in a 3x3 cube, only one cube is out of position, but in a 4x4 cube two cubes are out of position. In a 15 puzzle (the sliding puzzle where you try to put the ...

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Match the blocks
14 votes

I found a different way to solve it. Note that this doesn't disprove @trolley813's proof - it only shows one part of the proof is incorrect:

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Sliding Bolt Puzzle
13 votes

This is a supplemental to Kendall's answer that proves its correctness: Because there are four bolts, each with two possible positions, there are 24=16 states. You might think we'd want to categorize ...

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The LoL number game
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13 votes

First of all, notice that by repeatedly applying $\bf o$, we can always reduce a number to 2. This should be readily apparent, but here's a non-rigorous proof of the fact: 2 has a binary ...

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The Old Millionaire
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13 votes

For simplicity, I'm going to refer to the associates as knight, knave, and joker. Also, I'm assuming that they won't reveal the location of the money. If they did, then obviously you would switch to ...

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The Ball Factory Worker
13 votes

Let's lay down some groundwork to help us out: Let $req(n, d)$ be the number of digit $d$ required to write out all the numbers from 1 to $n$. Since each kit contains two of each digit, we have $2n$ ...

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Ten distinct numbers in the table
12 votes

As @xnor said, we can show it is not possible by using a parity argument. Let's look at a few examples of smaller tables to illustrate the argument. Let's start with the obviously impossible 2x2: 0 1 ...

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Linesweeper (Knight)
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12 votes

Here's the path (in green): My first step was to go through each one and mark (in orange) all the squares that could be seen by a zero. I marked the question mark and zero clues in red to help me ...

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What is twice the answer to this question?
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12 votes

Given that your question is self referential and requests twice its own answer, we need something that is twice itself. Zero works - two times zero is still zero, so if the answer to your question is ...

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First number, which can not be defined
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12 votes

There is no such number. Like Ross mentioned in his answer, this is related to Richard's paradox. At the heart of both this puzzle and Richard's paradox is (from the Wikipedia article) the ...

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How can our secret agent produce a cryptographically secure random number?
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11 votes

Easy: How does this guarantee that the message will not be decodable?

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Barely Illegal Rubik's Cube State
9 votes

Here's one way to show the cube cannot be solved: Suppose the bottom face is white. Then the corner piece with yellow and white visible is in the right place, and is the fourth blue corner. That means ...

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Not enough pylons!
9 votes

This might work: If Bob's boss is predictable, Bob can plan (or pretend) to This way, his boss will not know that only 50 pylons were used. It would be reasonable to assume that either 50 pylons ...

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The Answer is in the Question…
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9 votes

Answer: Explanation:

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About Grelling's Paradox
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8 votes

There is no paradox as long as you realize that, when you say "all adjectives can be categorized as autological or heterological", the "or" is not exclusive. To explain this a little bit better, let'...

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The Maze With An Unknown Size
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8 votes

How can you assure you get in the shortest amount of time? Unfortunately, if you know nothing about the design of the maze, then there is no optimal strategy. For example, it would be easy to design ...

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Who Married Whom and When?
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7 votes

I believe the twist here is that: Why do we need the twist? From there Now that we have some possibilities established for that person, let's move on to another one. We now know who is married to ...

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Finding the Dr. Bronowski's number
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7 votes

The smallest number I could find is My process for finding it: An example of my process: UPDATE: Here's a number that is smaller that almost works: It doesn't quite work because the number ...

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Variants to blue eyes puzzle
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7 votes

Variant 1: The oracle saying "not everyone has blue eyes" does not add any information here. Consider the case where there are only two people on the island, one of whom has blue eyes and the other ...

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Recover the Ripped Quote
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7 votes

This is what was written on the paper: The quote is: How I figured this out:

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Blue eyes riddle: a counter-argument to accepted solution
6 votes

Your "parallel induction" is already happening in the generally accepted solution When the solution says "A considers that B considers that ...", B, C, and so on are all arbitrary people. So ...

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What's the optimal score in the MU-game?
6 votes

Mary will win 2 Euros if both of them play optimally. Frodoskywalker has given a strategy that Mary can use to accomplish this. Here's why this will happen: Mary will write down 41 M's, and Ursula ...

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What is the next number in this sequence?
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6 votes

The numbers represent The next 5 numbers are

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Who is the thief? An elementary school teacher had her purse stolen
6 votes

Like @dmg said, the culprit is I used a slightly different path to come to this conclusion, though:

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Dominating Furbles
6 votes

I assume that this question is asking what a stable ratio of dominators to sharers is. I'm also going to assume that their strategy comes from their parent (otherwise there's definitely not enough ...

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Tiling three pears with three-pair hexominos
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5 votes

Here is the finished tiling: To get started: Next step: Looking at the left pear: With those chokepoints: For the next step I took a guess: From there, I just looked at the pieces I had left and ...

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