## Search found 284 matches

- Wed May 16, 2007 8:07 pm UTC
- Forum: Coding
- Topic: Does anyone here compete on Topcoder?
- Replies:
**30** - Views:
**14923**

There's solved and 'solved'. There are LOTS of ways to 'solve' a problem, but a decent solution can be harder to find. Sort of like that 'OMGWTF' contest, you can satisfy the submission by simply sticking the correct operations into the stubbed out functions. That won't win, and it's not what the p...

- Wed May 09, 2007 2:59 pm UTC
- Forum: Logic Puzzles
- Topic: Tic-tac-toe variant
- Replies:
**2** - Views:
**2192**

- Wed May 09, 2007 2:44 pm UTC
- Forum: Mathematics
- Topic: Trigonometry Joke
- Replies:
**15** - Views:
**7724**

- Thu May 03, 2007 4:17 pm UTC
- Forum: Mathematics
- Topic: The number i
- Replies:
**57** - Views:
**18322**

Regarding i in physics, I don't know of anywhere in physics where you actually need i. It certainly is very useful, for example in quantum mechanics, but eventually, you only measure real numbers, and you an do all of the calculations using real numbers. Regarding real numbers in physics, I don't k...

- Wed May 02, 2007 3:37 pm UTC
- Forum: Mathematics
- Topic: Duplicate Bananas
- Replies:
**37** - Views:
**8647**

- Mon Apr 30, 2007 12:48 pm UTC
- Forum: Logic Puzzles
- Topic: Chess Game [solution discussion]
- Replies:
**11** - Views:
**4897**

Umm... I thought the original question stated that the checkmate move occurred on the 5th move of the game. The 5th move is taken by white, not black, and it's only his 3rd move of the game... seems impossible given the constraints. Okay, I admit that if you consider that a checkmate via knight cap...

- Tue Apr 17, 2007 4:20 pm UTC
- Forum: Logic Puzzles
- Topic: A question more than a puzzle
- Replies:
**60** - Views:
**11614**

- Fri Apr 13, 2007 3:43 pm UTC
- Forum: Logic Puzzles
- Topic: 12 marbles and a scale....kinda like 8
- Replies:
**15** - Views:
**4552**

- Thu Apr 12, 2007 4:00 pm UTC
- Forum: Logic Puzzles
- Topic: Digits
- Replies:
**32** - Views:
**5728**

The only way you're going to win on this one is when the amount of data given is so lengthy that the generative rule is simpler than the restatements that Yakk and I have given. Which isn't too hard; but it will take more than 6 data points. Actually it's very easy to 'win': Tally all of the thread...

- Wed Apr 11, 2007 11:47 pm UTC
- Forum: Logic Puzzles
- Topic: Digits
- Replies:
**32** - Views:
**5728**

- Tue Apr 10, 2007 4:11 am UTC
- Forum: Logic Puzzles
- Topic: Digits
- Replies:
**32** - Views:
**5728**

Just be careful with your equals signs, dude. It would have been better to say something like, L(1) = 3 L(2) = 3 L(3) = 5 L(4) = 4 L(5) = 4 L(6) = 3 What is L(7)? The problem, of course, is that I can construct a polynomial that has the proper L(i) for each i given, and has whatever L(7) I want it ...

- Mon Apr 09, 2007 9:38 pm UTC
- Forum: Logic Puzzles
- Topic: Digits
- Replies:
**32** - Views:
**5728**

- Mon Apr 09, 2007 9:15 pm UTC
- Forum: Logic Puzzles
- Topic: Two numbers
- Replies:
**20** - Views:
**4216**

- Mon Apr 09, 2007 9:12 pm UTC
- Forum: Logic Puzzles
- Topic: Digits
- Replies:
**32** - Views:
**5728**

- Tue Apr 03, 2007 10:50 pm UTC
- Forum: Logic Puzzles
- Topic: Is this a question?
- Replies:
**41** - Views:
**8608**

### Re: Is this a question?

aarestad wrote:It's not even a sentence.

Why not? Wasn't that? Do you subscribe to a strange, restrictive definition of sentence with requirements divorced from actual practice?

There, there.

- Wed Mar 21, 2007 7:21 pm UTC
- Forum: Logic Puzzles
- Topic: Simplified luring lottery [solutions discussion]
- Replies:
**12** - Views:
**3829**

- Wed Mar 21, 2007 5:12 pm UTC
- Forum: Logic Puzzles
- Topic: Tetrahedral Volume [solution thread]
- Replies:
**9** - Views:
**4030**

- Wed Mar 21, 2007 4:53 pm UTC
- Forum: Logic Puzzles
- Topic: Simplified luring lottery [solutions discussion]
- Replies:
**12** - Views:
**3829**

To maximize the expected value of the prize, I tried differentiating the expected value and setting that equal to zero. Surprisingly something nice popped out, maybe someone should check my work: 1-(1-p)^N = N*p*E(p) where E(p) is the expected value of the prize (U=1) if everyone enters with probabi...

- Wed Mar 21, 2007 4:48 pm UTC
- Forum: Logic Puzzles
- Topic: Simplified luring lottery [solutions discussion]
- Replies:
**12** - Views:
**3829**

- Wed Mar 21, 2007 2:47 pm UTC
- Forum: Logic Puzzles
- Topic: Simplified luring lottery [solutions discussion]
- Replies:
**12** - Views:
**3829**

- Tue Mar 20, 2007 11:17 pm UTC
- Forum: Logic Puzzles
- Topic: Tetrahedral Volume [solution thread]
- Replies:
**9** - Views:
**4030**

### Tetrahedral Volume [solution thread]

Two non-adjacent edges... Okay, from an edge to a vertex is a bit longer, and from a vertex to a vertex a bit longer, so we'll estimate the side length to be 1.5 * 6 = 9. Then the base (one triangle) is area about 9*9sqrt(2)/2, which we'll say is like 81*3/4~=60. A cube with that base would be about...

- Tue Mar 20, 2007 7:50 pm UTC
- Forum: Logic Puzzles
- Topic: Simplified luring lottery [solutions discussion]
- Replies:
**12** - Views:
**3829**

### Re: Simplified luring lottery [solutions discussion]

Those were similar to my lines of thought. In fact we may be able to extract something nice if we can simplify your expected value expression: (C(N,1)*p*q^(N-1)+(1/2)*C(N,2)*p^2*q^(N-2)+(1/3)*C(N,3)*p^3*q^(N-3)+...+(1/n)*C(N,N)*p^N) =sum((1/k)*C(N,k)*p^k*(1-p)^(N-k),k=1..N) This is very close to a s...

- Tue Mar 20, 2007 3:42 pm UTC
- Forum: Logic Puzzles
- Topic: Simplified Luring Lottery
- Replies:
**1** - Views:
**2266**

### Simplified Luring Lottery

First assume superrationality, the idea that everyone knows that everyone knows that (etc) everyone is perfectly rational. Thus everyone ends up with the same strategy. Also assume no communication between participants. Here's the puzzle: I offer a prize of utility U to N of you. Your choices are a)...

- Wed Feb 28, 2007 1:17 am UTC
- Forum: Logic Puzzles
- Topic: Donuts Revisited
- Replies:
**4** - Views:
**2558**

- Wed Jan 31, 2007 4:06 am UTC
- Forum: Logic Puzzles
- Topic: Riddle I Came Up With- No Maths Required!
- Replies:
**29** - Views:
**8404**

The correct answer is an eight inch adjustable wrench. Proof: Google!

"To do this, remove the jaw from the wrench and grind one more notch on the â€œrackâ€

"To do this, remove the jaw from the wrench and grind one more notch on the â€œrackâ€

- Fri Jan 19, 2007 5:23 pm UTC
- Forum: Logic Puzzles
- Topic: Official xkcd puzzle [solution]
- Replies:
**14** - Views:
**5099**

- Fri Jan 12, 2007 3:24 am UTC
- Forum: Logic Puzzles
- Topic: pentagons inside of a triangle
- Replies:
**14** - Views:
**4389**

- Fri Jan 12, 2007 12:56 am UTC
- Forum: Logic Puzzles
- Topic: pentagons inside of a triangle
- Replies:
**14** - Views:
**4389**

- Tue Jan 09, 2007 12:23 am UTC
- Forum: Logic Puzzles
- Topic: [Solution] #6: Footsteps on the Tile
- Replies:
**5** - Views:
**2877**

rhino wrote:Or:

1:1, because there are countably infinitely many red squares, and countably infinitely many grey squares. Not only that, there are also countably infinitely many white squares, so the ratio white:red:grey is 1:1:1.

Instead use natural density or something.

- Tue Jan 09, 2007 12:21 am UTC
- Forum: Logic Puzzles
- Topic: #13: Them Speedy Steppe Flies
- Replies:
**19** - Views:
**6026**

### Re: #13: Them Speedy Steppe Flies

A fly is doomed to meet its gristly end between two very large trains in a very small tunnel. The two trains start at different ends of a 100 mile tunnel and move toward eachother each going 25 mph. The fly starts from one of the trains the instant it starts moving and can accelerate (and decelerat...

- Mon Jan 08, 2007 4:49 pm UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0207: "What xkcd Means"
- Replies:
**482** - Views:
**75038**

- Wed Dec 20, 2006 4:13 am UTC
- Forum: Logic Puzzles
- Topic: [Solution] #6: Footsteps on the Tile
- Replies:
**5** - Views:
**2877**

- Wed Dec 13, 2006 6:34 am UTC
- Forum: Logic Puzzles
- Topic: Infinite hats
- Replies:
**31** - Views:
**12375**

- Tue Dec 12, 2006 8:06 pm UTC
- Forum: Logic Puzzles
- Topic: Infinite hats
- Replies:
**31** - Views:
**12375**

Maybe it's just a matter of semantics, but I would say a strategy does exist (albeit an unusable one). Putting everything into a mathematical setting -- Let S be the set of all the logicians, h be an arbitrary function from S to {red,blue}, and R the set of all elements s in S such that h(s)=red. W...

- Tue Dec 12, 2006 5:30 pm UTC
- Forum: Logic Puzzles
- Topic: Infinite hats
- Replies:
**31** - Views:
**12375**

So there exists a strategy, but I doubt they can actually find it, given the non-constructive nature of the Axiom of Choice. I guess the question remains as to whether anyone can find a strategy, rather than just proving its existence. Surely a strategy that they can't actually use isn't actually a...

- Tue Dec 12, 2006 3:34 am UTC
- Forum: Logic Puzzles
- Topic: Infinite hats
- Replies:
**31** - Views:
**12375**

Pick number Check if number results in finitely many differences If it does, pick it, yell out choice If it doesn't, pick next number and repeat The only problem I see here, and the reason I almost didn't submit this, is that each logician is required to do potentially infinite work. This doesn't w...

- Mon Dec 11, 2006 11:28 pm UTC
- Forum: Logic Puzzles
- Topic: Sum of two sequences
- Replies:
**2** - Views:
**2388**

- Mon Dec 11, 2006 12:27 pm UTC
- Forum: Logic Puzzles
- Topic: Official xkcd puzzle [SOLUTIONS]
- Replies:
**47** - Views:
**83381**

I must admit I cannot rationalize F(34)=55 and F(35)=53. If those really are the correct values, I submit that my sequence F' is nicer, and more in keeping with the newly revealed comic (which is now outside my office). For 0<=x<=33 and x=71, F'(x)=F(x), but F'(34)=51 and F'(35)=49. F'(x) for 36<=x<...

- Sun Dec 10, 2006 1:17 am UTC
- Forum: Logic Puzzles
- Topic: Envelopes puzzle
- Replies:
**10** - Views:
**6104**

That x doesn't remain constant? Sure it does. If you like, open the first envelope. Say it contains $100. Now should you switch? Same logic: 50% chance the other contains $50, 50% chance it contains $200. So by switching you get expected value $50/2 + $200/2 = $125. But you'd have come to that conc...

- Tue Nov 28, 2006 11:52 pm UTC
- Forum: Logic Puzzles
- Topic: An Interesting Hypothesis [solution thread]
- Replies:
**1** - Views:
**2108**

### An Interesting Hypothesis [solution thread]

Of course, though I may drink hot chocolate right now, that does not prevent you from also drinking hot chocolate.