Build a monolith that will let light through in the pattern you want when the sun is in the right position in the sky.

Offer to set up a time capsule for an elementary school, then hide it with the kids messages for the future. Nobody will bother looking early.

## Search found 21 matches

- Sat Dec 21, 2013 1:52 pm UTC
- Forum: Serious Business
- Topic: Encode a message so it can't be read until a certain time?
- Replies:
**84** - Views:
**55287**

- Thu Nov 14, 2013 10:04 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 1289: "Simple Answers"
- Replies:
**50** - Views:
**11489**

### Re: 1289: "Simple Answers"

"'Will [ ] allow us to better understand each other and thus make war undesirable?'"

Optimistic "thus."

- Sun Jun 12, 2011 3:44 pm UTC
- Forum: Coding
- Topic: Logic Puzzle Solver
- Replies:
**1** - Views:
**2079**

### Logic Puzzle Solver

I have a coding question related to a personal project I have to build a logic puzzle solver for grid-based logic puzzles. To see a lot of examples of this kind of puzzle, look here: http://www.logic-puzzles.org/ First, some background: Let 'n' represent the number of categories in a logic puzzle, a...

- Mon Jun 06, 2011 2:55 pm UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0904: "Sports"
- Replies:
**128** - Views:
**30137**

- Mon Nov 15, 2010 10:35 pm UTC
- Forum: Logic Puzzles
- Topic: A very interesting Mathematical Paradox
- Replies:
**387** - Views:
**157993**

### Re: A very interesting Mathematical Paradox

Two numbers are equal if their difference is zero. How does this apply when one of the numbers is something weird with infinite non-zero digits, like 0.99999....? The way math guys usually deal with things like this is to say that 0.99999... is equal to 1 if, no matter how small a separation you giv...

- Fri Dec 04, 2009 6:26 am UTC
- Forum: Logic Puzzles
- Topic: 12 Craziest Google Interview Questions
- Replies:
**67** - Views:
**13665**

### Re: 12 Craziest Google Interview Questions

7. Assuming companies merge in pairs, and order matters: To save space, C(X,Y) = X Choose Y = X! / (Y! * (X-Y)!) First pair of companies can be chosen in C(N,2) ways 2nd pair of companies in C(N-1,2) ways (choosing 2 from the set of all N-2 remaining compa...

- Fri Apr 17, 2009 5:44 am UTC
- Forum: Logic Puzzles
- Topic: Traveler's Dilemma
- Replies:
**833** - Views:
**88495**

### Re: Traveler's Dilemma

lordatog wrote:And you still didn't answer my question.

Sorry not to have been clear.

$2 < $100

- Fri Apr 17, 2009 5:10 am UTC
- Forum: Logic Puzzles
- Topic: Traveler's Dilemma
- Replies:
**833** - Views:
**88495**

### Re: Traveler's Dilemma

The step in the "100 is optimal" strategy I have a problem with is the line "Given that you and your opponent are both going to pick the same number, which number is optimal?" That line implies that you can influence your opponent's choice by way of your choice but you can't. Of...

- Fri Apr 17, 2009 4:15 am UTC
- Forum: Logic Puzzles
- Topic: Traveler's Dilemma
- Replies:
**833** - Views:
**88495**

### Re: Traveler's Dilemma

Clearly you disagree with the above. What I really don't know is precisely which step you have a problem with. Let's suppose again that there is a unique, optimal strategy, X, and that you and your opponent are both perfectly rational, and both going to pick your numbers via strategy X. Fine. Given...

- Thu Apr 02, 2009 3:18 am UTC
- Forum: Logic Puzzles
- Topic: Self-Referential Aptitude Test
- Replies:
**1** - Views:
**1767**

### Self-Referential Aptitude Test

A friend just recommended this to me. I haven't solved it yet, but have been assured that there is a unique solution. SELF-REFERENTIAL APTITUDE TEST, by Jim Propp (propp@math.wisc.edu) The solution to the following puzzle is unique; in some cases the knowledge that the solution is unique may actual...

- Wed Apr 01, 2009 9:06 pm UTC
- Forum: Logic Puzzles
- Topic: The Sexaholics of Truthteller Planet
- Replies:
**15** - Views:
**2818**

### Re: The Sexaholics of Truthteller Planet

Well done!

Now, can you decode a word or phrase from your solution? There's a hint in the flavor text.

Now, can you decode a word or phrase from your solution? There's a hint in the flavor text.

- Wed Apr 01, 2009 11:08 am UTC
- Forum: Logic Puzzles
- Topic: Three princesses
- Replies:
**446** - Views:
**206863**

### Re: Three princesses

Greyson wrote:But you might ask the middle child.

**Spoiler:**

- Wed Apr 01, 2009 10:53 am UTC
- Forum: Logic Puzzles
- Topic: The Sexaholics of Truthteller Planet
- Replies:
**15** - Views:
**2818**

### Re: The Sexaholics of Truthteller Planet

This doesn't affect the day 1 analysis, but is it correct to assume that if an individual is infected, they remain infected over the course of the puzzle, and if an individual is uninfected, they remain uninfected over the course of the puzzle? Yes; that was specified in the original post (which is...

- Wed Apr 01, 2009 2:46 am UTC
- Forum: Logic Puzzles
- Topic: The Sexaholics of Truthteller Planet
- Replies:
**15** - Views:
**2818**

### The Sexaholics of Truthteller Planet

This puzzle is from the 2009 MIT Mystery Hunt. It's the hardest example of this kind of logic puzzle I've ever seen. Check out this link for more 2009 Hunt puzzles: http://web.mit.edu/puzzle/www/09/puzzles/ Any other Hunters out there? Anyway, here's the puzzle. Note that as with most Hunt puzzles, ...

- Tue Mar 31, 2009 3:47 am UTC
- Forum: Logic Puzzles
- Topic: Word Chain
- Replies:
**86** - Views:
**9921**

### Re: Word Chain

Zak wrote:Edit: Whoops, just realized that that was from the first page...Erm,Spoiler:

Glass -> Fly

**Spoiler:**

- Tue Mar 31, 2009 3:20 am UTC
- Forum: Logic Puzzles
- Topic: Three princesses
- Replies:
**446** - Views:
**206863**

### Re: Three princesses

**Spoiler:**

- Sun Mar 29, 2009 2:49 pm UTC
- Forum: Logic Puzzles
- Topic: Traveler's Dilemma
- Replies:
**833** - Views:
**88495**

### Re: Traveler's Dilemma

I think that they would both reason like this: Aha! I've seen this before.This is one of those puzzles where a series of seemingly optimal choices leads us to get almost nothing. If I know that, so must my traveling companion. We're going to come to the same conclusion about either playing this ruin...

- Sun Mar 29, 2009 2:35 pm UTC
- Forum: Logic Puzzles
- Topic: Three princesses
- Replies:
**446** - Views:
**206863**

### Re: Three princesses

Ask A: "Is it true that A is the eldest and B is the middle, or that A is the youngest and B is the eldest?" Case: A eldest, B middle: answer is true, A says 'yes' Case: A youngest, B eldest: answer is true, A says 'no' Case: A eldest, B youngest: answer is false, A says &...

- Sun Mar 29, 2009 6:39 am UTC
- Forum: Logic Puzzles
- Topic: Describing numbers...
- Replies:
**65** - Views:
**20305**

### Re: Describing numbers...

The answer is either '1' (though it could be expressed in 'fewer' than seventeen words in standard English) or 'no answer' if we replace 'less' with 'fewer' because were such a number to exist, the phrase: 'The smallest natural number that cannot ...

- Sun Mar 29, 2009 5:56 am UTC
- Forum: Logic Puzzles
- Topic: Three princesses
- Replies:
**446** - Views:
**206863**

### Re: Three princesses

Right. Ask A whether B would say C is the youngest. If you're asking the eldest and C is the middle, she'll say 'yes'; if you're asking the youngest and C is the middle, she'll say 'yes.' So ask the question, if you get a 'yes' marry B, and if you get a '...

- Sun Mar 29, 2009 5:39 am UTC
- Forum: Logic Puzzles
- Topic: Three princesses
- Replies:
**446** - Views:
**206863**

### Re: Three princesses

You ask: "Is the middle princess going to answer this truthfully, or are you the youngest princess? If asked to the eldest, the true answer is 'no,' so she says 'no.' If asked to the youngest, the true answer is 'yes,' so she says 'no.' If asked to the middle pr...