## Search found 284 matches

Mon Mar 07, 2016 6:38 pm UTC
Forum: Logic Puzzles
Topic: Logic puzzles beta testing
Replies: 4
Views: 2535

### Re: Logic puzzles beta testing

Either you have a typo or the puzzle admits multiple solutions. Either is possible.
Sun Mar 06, 2016 8:38 pm UTC
Forum: Logic Puzzles
Topic: Logic puzzles beta testing
Replies: 4
Views: 2535

### Logic puzzles beta testing

Three friends and I are writing some puzzles for the Microsoft Puzzle Hunt (https://en.wikipedia.org/wiki/Microsoft_Puzzle_Hunt). We're looking for beta testers. In particular 2 of our puzzles are good solid logic types and would definitely appeal to folks on these boards, though we have another 6-8...
Thu Nov 17, 2011 2:39 am UTC
Forum: Logic Puzzles
Topic: 3 heroes with hats vs a villain
Replies: 54
Views: 15463

### Re: 3 heroes with hats vs a villain

xkcdfan wrote:Does the villain have to be informed honestly of the strategy?

Um, yes? "our strategy is Alice will guess red", then Alice guesses blue.
Wed Oct 26, 2011 12:01 am UTC
Forum: Logic Puzzles
Topic: 2 jars of candy
Replies: 5
Views: 2552

### Re: 2 jars of candy

Wolfram Alpha can do it even if Google can't! And you're right, the difference is exactly in whether we stop when emptying a salt shaker or when first trying to use a previously emptied salt shaker.
Tue Oct 25, 2011 4:57 pm UTC
Forum: Logic Puzzles
Topic: 2 jars of candy
Replies: 5
Views: 2552

### Re: 2 jars of candy

1) I get about 11.2 pieces left: 2*(1/2)*2^(-99)*sum((100-k)*binomial(99+k,k)*2^(-k),k=0..99) and by simulation. Edit: 2) Looks like if both jars have equal pieces of candy then as N grows large the expectation of the remaining pieces is appro...
Wed Sep 07, 2011 11:26 pm UTC
Forum: Mathematics
Topic: An interesting topic for a math talk
Replies: 8
Views: 1941

### Re: An interesting topic for a math talk

Plan your presentation to last for 35 minutes with three breaks for questions and making sure everyone is following, one after 10 minutes, one after 20 minutes, and one at the end. Practice giving your presentation at least once. These two steps will improve your talk more than selecting a good topi...
Sat Aug 20, 2011 5:10 pm UTC
Forum: Mathematics
Topic: Weighted coin question and probability
Replies: 10
Views: 1924

### Re: Weighted coin question and probability

Edit: I didn't answer your 6-heads question, modified to "I flip a coin 3 times and get 3 heads. What is the probability it's a weighted coin?" instead. Bayesian: start with your current belief, which for a random coin found in your change normally looks something like "the coin flips...
Tue May 17, 2011 5:26 pm UTC
Forum: Science
Topic: Dolphin in a hamster ball
Replies: 25
Views: 2909

### Re: Dolphin in a hamster ball

bigglesworth wrote:Clearly the only interesting permutation of this problem is the one with the ball being permeable to gas but not liquid, the sphere having a fair amount of air in it, and the dolphin-ball rolling around in a park chasing people.

Yes, this was the motivating scenario.
Mon May 16, 2011 5:17 am UTC
Forum: Science
Topic: Dolphin in a hamster ball
Replies: 25
Views: 2909

### Dolphin in a hamster ball

If you put a dolphin in a giant ball with water inside, would that work?
Tue Jun 02, 2009 8:53 am UTC
Forum: Logic Puzzles
Topic: Camels and Bananas
Replies: 27
Views: 4901

### Re: Camels and Bananas

A 4-camel in a 4-desert can get 2 bananas to the other side and come back, leaving an empty desert, as follows: A(2/4): 4 bananas distance 1, drop 2 off, return. This deposits 2 bananas at distance 1. B(6/4): A, then bring 4 for 1 unit, grab a new banana, go another unit, drop off 2...
Mon Jun 01, 2009 3:21 am UTC
Forum: Logic Puzzles
Topic: Camels and Bananas
Replies: 27
Views: 4901

### Re: Camels and Banans

assuming that you can drop the bananas and come back like silvermace said, i think i have solved it: 833 bananas At first what you have to do is take three trips for every one unit you move. So for every one unit the bananas travel, you lose 3 bananas. As long as you have over 2000 bananas to move,...
Sun May 31, 2009 5:09 am UTC
Forum: Logic Puzzles
Topic: Biggest value
Replies: 27
Views: 3161

### Re: Biggest value

In order to say that BB(100) is computable, don't you have to be able to compute the actual value of BB(100)? No. Just like my claim that the 2^10000th prime is odd, the claim that BB(100) is computable is true regardless of whether I know which integer is the 2^10000th prime or which integer is BB...
Sun May 31, 2009 4:09 am UTC
Forum: Mathematics
Topic: Statistics - measure of overlap between populations?
Replies: 2
Views: 504

### Re: Statistics - measure of overlap between populations?

...what? What are you actually trying to find? |A intersect B| is the number of mutual friends A and B have, done. Why are you dividing by anything? If you want to exclude some people ("friend-collectors") from the domain, just exclude them. chi-squared tests? Clearly you haven't told us w...
Tue May 05, 2009 7:54 pm UTC
Forum: Mathematics
Topic: Probability Question
Replies: 6
Views: 623

### Re: Probability Question

Unconventional solution: Google "65780 cards", click on the link that talks about dealing cards from a deck, find the comment with the number you're interested in, see what the comment has to say.
Wed Apr 29, 2009 3:11 pm UTC
Forum: Mathematics
Topic: Simulate dice rolls
Replies: 9
Views: 1405

### Re: Simulate dice rolls

Box-Muller transform. Pseudo-code: roll(dice, sides) mean = (sides+1)/2.0; variance = (sides+1)*(2*sides+1)/6.0 - mean*mean; mean /= dice; variance /= dice; sum = floor(normalboxmuller(mean,variance) + 0.5); //add the 0.5 so that e.g. values from 34.5 to 35.5 are counted as 35 return sum; normalbox...
Fri Apr 24, 2009 9:23 pm UTC
Forum: Mathematics
Topic: Optimization problem.
Replies: 8
Views: 670

### Re: Optimization problem.

Hint #1: b does not appear in the expression you gave.
Sun Apr 12, 2009 9:01 am UTC
Forum: Logic Puzzles
Topic: Lottery
Replies: 16
Views: 2497

### Re: Lottery

This is similar to a real problem I encountered today. Suppose you have a hidden prize, and a group of people who will form teams to search for it. The fraction of the people who are on your team is the probability your team will find it, but the prize is always divided evenly among all the players...
Mon Apr 06, 2009 6:54 am UTC
Forum: Mathematics
Topic: Spheres and cubes in high dimensions
Replies: 7
Views: 910

### Re: Spheres and cubes in high dimensions

I assume the answer is 0 but haven't done any work at all. Actually I'd say my priors are around 90% 0, 9% 1, and 1% something else.

ETA: Sweet, looks like the answer is going to be surprising.
Sun Apr 05, 2009 4:59 am UTC
Forum: Mathematics
Topic: [Question] Random Numbers & Expected Stddev
Replies: 5
Views: 821

### Re: [Question] Random Numbers & Expected Stddev

Oh I see, yes, I missed that you had canceled the 2y and 1/2y. We agree, that seems to be the only difference.
Sun Apr 05, 2009 4:32 am UTC
Forum: Mathematics
Topic: [Question] Random Numbers & Expected Stddev
Replies: 5
Views: 821

### Re: [Question] Random Numbers & Expected Stddev

Why does "a single number from U[-y,y] have mean 0 and stddev sqrt((y^2 + y) / 3)"? From this formula, I get that the stddev should be \sqrt{\frac{1}{2y}\sum _{i=-y}^y i^2} = \frac{\sqrt{(1+y) (1+2 y)}}{\sqrt{6}} . Let's see... first off, that should be 1/(2y+1) instead of...
Sun Apr 05, 2009 2:11 am UTC
Forum: Mathematics
Topic: What would I get in discrete math?
Replies: 15
Views: 1925

### Re: What would I get in discrete math?

Counting and probability are phenomenal. The best evar.
Sun Apr 05, 2009 2:09 am UTC
Forum: Mathematics
Topic: [Question] Random Numbers & Expected Stddev
Replies: 5
Views: 821

### Re: [Question] Random Numbers & Expected Stddev

A single number from U[-y,y] has mean 0 and stddev sqrt((y^2 + y) / 3). Summing x of these gives approximately a normal random variable with stddev sqrt(x) times the individual stddevs. The expected standard deviation should be pretty close to this, and it almost agrees with your result: sqrt(1/3) *...
Sat Mar 21, 2009 2:16 am UTC
Forum: Logic Puzzles
Topic: A Frozen Crowd
Replies: 4
Views: 1808

### Re: A Frozen Crowd

I think creators should be pressured to create artifacts which are not as Googlable as riddles.
Sat Mar 07, 2009 10:26 pm UTC
Forum: Mathematics
Topic: how do I solve these number sequences?
Replies: 19
Views: 3766

### Re: how do I solve these number sequences?

Sequence problems are pointless. ...what Sequence problems are incredibly useful. They develop your intuition for finding good abstractions from a finite set of numbers. "Sequence problems" come up all the time in the (combinatorial subset of) the real world. Are you upset because there i...
Fri Feb 20, 2009 4:29 pm UTC
Forum: Mathematics
Topic: The Theorem Thread
Replies: 15
Views: 1875

### Re: The Theorem Thread

A polyhedron must have a pair of faces with the same number of edges. Each face must have at least 3 edges. Since no two edges of a face are shared by the same other face, each face must have at most F-1 faces, for a polyhedron with F faces. So each face has between 3 and F-1 faces, and there are at...
Thu Feb 12, 2009 8:02 pm UTC
Forum: Mathematics
Topic: Favorite math jokes
Replies: 1452
Views: 459636

### Re: Math joke

Buttons wrote:
Nlelith wrote:This might work on a T-shirt if you have an imaginary function become real (too lazy to think of an example but you know what I'm getting at) and underneath have it read "shit just got real."

Thus?

I would purchase that shirt.
Tue Feb 03, 2009 6:45 am UTC
Forum: Logic Puzzles
Topic: 3AM thought
Replies: 4
Views: 1474

### Re: 3AM thought

Note: There are no right or wrong answers, at long as it's reasonable. Yes, there are wrong answers. For example, "Obama won, and that's the way it is." is a wrong answer. Either "the only two possible outcomes" in the original question has some coherent, useful meaning, in whic...
Wed Jan 28, 2009 12:57 am UTC
Forum: Mathematics
Topic: Massively Collaborative Mathematics
Replies: 20
Views: 2081

### Massively Collaborative Mathematics

Keep an eye on this, when Gowers gets his problem up I have a feeling there are a number of people here who will want to participate!

Massively Collaborative Mathematics

Edit: spelled his name wrong.
Sat Jan 17, 2009 9:57 pm UTC
Forum: Mathematics
Topic: .
Replies: 11
Views: 1390

### Re: Relearning the Basics

The correct answer is look up state standards for mathematics from elementary to high school, then go through grade by grade finding things that review each concept. Pick a state, any state.
Tue Jan 13, 2009 6:57 am UTC
Forum: Mathematics
Topic: common error in poker logic?
Replies: 17
Views: 2029

### Re: common error in poker logic?

The turn comes 7, the river comes 7. Now do you think it's less likely your opponent holds a 7?
Sat Dec 13, 2008 10:34 pm UTC
Forum: Logic Puzzles
Topic: Outsmarting the Genie
Replies: 257
Views: 22768

### Re: Outsmarting the Genie

I don't understand this genie. If he has so much power why doesn't he just go torture someone? Anyway, my three wishes: 1. Genie! Correctly compute the coherent extrapolated volition of { humans } U { you } if possible! 2. Genie! If counterfactually my third wish was "Give me a giant robot vers...
Thu Nov 20, 2008 3:08 am UTC
Forum: Mathematics
Topic: Bayesian vs Frequentist : the Final Showdown!!
Replies: 39
Views: 4848

### Re: Bayesian vs Frequentist : the Final Showdown!!

jestingrabbit wrote:Although this seems to be an attractive avenue, Jaynes and I agree that its not as useful as it seems.

Spoiler:
Yeah but he doesn't get to that 'til like chapter 18 or something!
Wed Nov 19, 2008 7:47 pm UTC
Forum: Gaming
Topic: Warlocks (Spellcaster, Waving Hands, etc)
Replies: 169
Views: 13978

### Re: Warlocks (Spellcaster, Waving Hands, etc)

I'm fine with not communicating regarding big strategy discussions, but what about noting who you're targeting with a counterspell/mindspell to avoid cancellation? That just takes a PM using the extant Warlocks "you can send one note to a person at a time" system.
Wed Nov 19, 2008 7:35 pm UTC
Forum: Mathematics
Topic: Bayesian vs Frequentist : the Final Showdown!!
Replies: 39
Views: 4848

### Re: Bayesian vs Frequentist : the Final Showdown!!

Bayesians think that an assignment of probabilities is a statement about beliefs. Ah, that makes sense. The problem is that some Bayesian mathematics is predicated on bad beliefs -- like "if we know nothing, we should assume uniform probabilities"? Suppose we have a basket of balls. We kn...
Wed Nov 19, 2008 5:14 pm UTC
Forum: Gaming
Topic: Warlocks (Spellcaster, Waving Hands, etc)
Replies: 169
Views: 13978

### Re: Warlocks (Spellcaster, Waving Hands, etc)

All right! What are the rules for this thing? Should we communicate, only communicate via a shared forum (like this thread), not communicate at all? The winner is the last team with someone left standing?
Mon Nov 17, 2008 11:14 pm UTC
Forum: Mathematics
Topic: Bayesian vs Frequentist : the Final Showdown!!
Replies: 39
Views: 4848

### Re: Bayesian vs Frequentist : the Final Showdown!!

The question for things that have ALREADY happened (my friend is either dead or he isn't, whichever one is ACTUALLY TRUE, you either have a cat or a rhinoceros) is "How certain can we be that X is true?" "We can be 50% certain that Goplat owns a cat." And the "Bayesians&quo...
Mon Nov 17, 2008 9:48 pm UTC
Forum: Mathematics
Topic: Bayesian vs Frequentist : the Final Showdown!!
Replies: 39
Views: 4848

### Re: Losing Your Marbles

There is no justification for assigning a uniform distribution on anything when the problem doesn't say so. Sometimes it'll give you something ridiculous: "Goplat's pet is either a cat or a rhinoceros. What is the probability that it's a rhino?" Uniform distribution says 1/2. Sometimes it...
Mon Nov 17, 2008 7:26 pm UTC
Forum: Mathematics
Topic: Bayesian vs Frequentist : the Final Showdown!!
Replies: 39
Views: 4848

### Re: Losing Your Marbles

I'm actually more persuaded by the Bayesian position myself (the probability is 1/3) than the frequentist position (the probability is inherently unknowable), but I can see that both positions have some merit. Awesome. I see the clear utility of using the Bayesian definition of probability and have...
Sat Nov 15, 2008 1:20 am UTC
Forum: Gaming
Topic: Warlocks (Spellcaster, Waving Hands, etc)
Replies: 169
Views: 13978

### Re: Warlocks (Spellcaster, Waving Hands, etc)

Yes, I've been wanting to try a team game for a while. Count me in. --Maknud
Thu Nov 13, 2008 6:22 pm UTC
Forum: Logic Puzzles
Topic: One Million Miles on Your Odometer
Replies: 12
Views: 2120

### Re: One Million Miles on Your Odometer

Google the answer to this Car Talk puzzler.

Go to advanced search