## Search found 81 matches

Sun Nov 23, 2008 11:16 pm UTC
Forum: Mathematics
Topic: Complex analysis Homework
Replies: 9
Views: 2105

### Re: Complex analysis Homework

Cconway; IV. 5.9 eh? You could've just asked someone here (on campus). We've taken the course already ;) So essentially you just want to show that f is analytic on a region containing [-1,1], right? Take an open disc containing it, and a triangular curve in there. If it doesn't intersect (or contain...
Sat Nov 15, 2008 9:06 am UTC
Forum: Logic Puzzles
Topic: Tetris Puzzle
Replies: 13
Views: 3893

### Re: Tetris Puzzle

Hold features still won't help you against a series of S's and Z's. Those guys will wipe you out. On that note, and while we're still far off-topic here, I was really displeased with a recent Tetris game I played. Aside from giving previews of pieces and having a hold feature, pieces could be flippe...
Thu Nov 13, 2008 7:26 am UTC
Forum: Logic Puzzles
Topic: Rubik's Sudoku 2
Replies: 3
Views: 1160

### Re: Rubik's Sudoku 2

Reformulation: assign to each colour a number, 1-9. Then what you would like is a 9x9 grid with two numbers (i,j) in each place, no (i,j) used more than once, and each row, column and 3x3 primary square containing distinct i's and j's. It's easy to build one by left shifting the i's and right shifti...
Thu Dec 13, 2007 3:41 pm UTC
Forum: Logic Puzzles
Topic: Help me stop a alien invasion.
Replies: 57
Views: 11282

### Re: Help me stop a alien invasion.

This sounds like the kind of problem you could solve with Desktop Tower Defense strategies. Play that game for a bit, and then you'll know that the best (most enjoyable?) solution is turrets, as they can stop a wide range of alien lifeforms. I've even seen evidence that they can keep the threat at b...
Thu Dec 13, 2007 3:31 pm UTC
Forum: Logic Puzzles
Topic: The Probability of a Pie Eating Contest
Replies: 11
Views: 2026

### The Probability of a Pie Eating Contest

36 people are to be divided into 6 groups of 6 to compete in an eating competition. 11 of these people are members of the local Amazing Eaters club. If 5 or more members of one group are Amazing Eaters, then that group will demolish any with fewer Amazing Eaters. What is the probability that a rando...
Thu Dec 13, 2007 1:47 pm UTC
Forum: Mathematics
Topic: Number Theory exam
Replies: 13
Views: 1824

### Re: Number Theory exam

Here's a funny one we got on the last day of class last year: The Sultan and Omar. The Sultan said to Omar, "I have three siblings. The sum of their ages is your age, and the product of their ages is the number of rooms in my palace. Figure out how old they are." (As everyone knows, the Su...
Thu Dec 13, 2007 1:44 pm UTC
Forum: Mathematics
Topic: Number Theory exam
Replies: 13
Views: 1824

### Re: Number Theory exam

Here's some from a 310 Final from 1992: 1) Find all integer solutions to 56x + 63y = 21 6) Characterize the odd primes p for which 7 is a square (mod p) 7) List the primitive roots mod 19. 8) Show that the Dirichlet product of (the Euler function) and (the number of divisors of n) is (the sum of the...
Wed Dec 05, 2007 9:56 pm UTC
Forum: Mathematics
Topic: Project Euler 20
Replies: 22
Views: 7843

### Re: Project Euler 20

yep this idea reduce number of possible value of SOD(100!), SOD(100!) < SOD(10^99) < 99*9 = 891 so we search a three digit number less than 891 that divisible by 9. it would be so easy if the question is SOD(SOD(100!)): because that positive number < 18 and divisible by 9, it much be 9. Careful aro...
Wed Dec 05, 2007 9:05 pm UTC
Forum: Mathematics
Topic: Elementary Money Problem
Replies: 8
Views: 1660

### Re: Elementary Money Problem

Is every transaction a Paypal transaction? Somebody needs to tell the guy at the end that he's just causing problems, or they need to meet up and use real money.
Tue Dec 04, 2007 1:42 am UTC
Forum: Mathematics
Topic: William Lowell Putnam Competition
Replies: 73
Views: 9054

### Re: William Lowell Putnam Competition

3.14159265... wrote:
Um. 10x+1?
BaldAdonis, I don't think our buddy will be happy about that one.

What's worse are the other ones, like ((9x+1)2-1)/9. At least he'd get part marks for saying they were all linear.
Sun Dec 02, 2007 6:49 am UTC
Forum: Mathematics
Topic: William Lowell Putnam Competition
Replies: 73
Views: 9054

### Re: William Lowell Putnam Competition

Primarily, does anyone know if the solution for the hyperbola one is actually 'Area=4,' or if that's just the "obvious" wrong answer? Just show that if there are more than one point in the set on any branch, then it can be reduced to one point, and then that if that one point A is not (1,...
Sun Dec 02, 2007 6:31 am UTC
Forum: Mathematics
Topic: William Lowell Putnam Competition
Replies: 73
Views: 9054

### Re: William Lowell Putnam Competition

For A3(the repunit one), did anyone get that there were an infinte amount of f's? I figured that if you multiply n by a power of 10 and then add ("said power of ten" - 1)/9 you would get another larger repunit. Because the repunit is an integer you don't have to worry about decimals... ri...
Sun Dec 02, 2007 2:08 am UTC
Forum: General
Topic: On kids, and beating the living shit out of them
Replies: 62
Views: 6148

### Re: On kids, and beating the living shit out of them

You should've told me, I was going to the library.
Sun Dec 02, 2007 2:04 am UTC
Forum: Mathematics
Topic: William Lowell Putnam Competition
Replies: 73
Views: 9054

### Re: William Lowell Putnam Competition

3.14159265... wrote:I got A3, and B1....

I think I messed up B2. That triangle solution doesn't work unless f(0)=0, but you know that for some x, f(x)=0, so I could've fixed it. This is the worst part of the Putnam: the long walk home when you pick apart your answers and find the mistakes.
Mon Mar 26, 2007 6:30 pm UTC
Topic: eating meat
Replies: 1333
Views: 148102
Why would not eating meat be morally superior? It assumed either that: Existance of an animal is naturally an unhappy process, ie a cow is happier never existing than ever existing or Simply eating meat, the act of consuming muscle(usually muscle atleast), is imoral. New idea: eating meat (via curr...
Sat Feb 17, 2007 8:31 am UTC
Forum: Logic Puzzles
Topic: Problem That Came Up in a Stats Class (Solution)
Replies: 4
Views: 2571
The solution you want is the Stirling numbers of the second kind, but with sets distinct. Look them up, but as I recall, you need a summation or a recursion to describe them: S(n, m) = (1/m!)([Sum i=1,...,m] (-1)^(m-i) (m choose i) (i^n), so you'll want F(n, m)=([Sum i=1,...,m] (-1)^(m-i) (m choose ...
Mon Jan 29, 2007 7:37 am UTC
Forum: Logic Puzzles
Topic: Riddle I Came Up With- No Maths Required!
Replies: 29
Views: 8397
How about a bookmark? I use those everyday, and often rip one in half to use in two books.

Seems the problem (advantage?) of non-maths/logic puzzles is the number of possible solutions. Everyone could come up with a viable answer without ever hitting the solution intended by the riddler.
Sat Jan 20, 2007 12:59 am UTC
Forum: Logic Puzzles
Topic: Official xkcd puzzle [solution]
Replies: 14
Views: 5099
Didn't mean to hash this all up again. There is already an extensive solution thread. I just wanted to know which was deemed the most elegant.
Fri Jan 19, 2007 5:48 am UTC
Forum: Logic Puzzles
Topic: Official xkcd puzzle, free shirts for solutions
Replies: 15
Views: 39684
So..... who won?
Sun Jan 14, 2007 8:44 am UTC
Forum: Logic Puzzles
Topic: Petals Around the Rose
Replies: 35
Views: 11093
Of course, but BaldAdonis' method works also. Somehow... Here's how: Since 1, 2, 4, and 6 all give zero, write out (x-1)(x-2)(x-4)(x-6). The values 3 and 5 give 6 and -12 respectively, which is lucky, because otherwise I'd have to add another power of x to make it all scale properly. In this case, ...
Sun Jan 14, 2007 8:31 am UTC
Forum: Logic Puzzles
Topic: Rulebreaker(New!)
Replies: 30
Views: 9148
Note that the same words get different album titles, as in the two cases of "I think i get it Geese fly sideways in autumn." Or even multiple lines in the same post, like SpitValve 's. And oddly enough, "No Code" never appears. I didn't much like that one myself, but it is a bit ...
Sat Jan 13, 2007 4:34 am UTC
Forum: Logic Puzzles
Topic: Petals Around the Rose
Replies: 35
Views: 11093
Blayze, how's this:
f(x)=|(x^4 - 13x^3 + 56x^2 - 92x + 48 )/3|
for each die with x from {1, 2, 3, 4, 5, 6}, and the score is the sum over all 5 values.
Wed Jan 10, 2007 6:08 am UTC
Forum: Logic Puzzles
Topic: Petals Around the Rose
Replies: 35
Views: 11093
I think this Lloyd Borrett should rewrite the program to remove a few combinations. The game gave itself away after just a couple rolls when I got one worth 0 and one worth 18.
Fri Dec 29, 2006 11:51 pm UTC
Forum: General
Topic: Popular Communism (Split from Nerdy Pet Peeves)
Replies: 17
Views: 4575
Since it was mentioned, I'd like to note that The Rebel Sell is a great read, and I'd recommend it to anyone who complains about counter culture high school kids, or the kids themselves, and especially Canadians.
Fri Dec 22, 2006 5:34 pm UTC
Forum: Logic Puzzles
Topic: Sequence: 15, 14, 5...
Replies: 3
Views: 3054
I'm working this out by hand, so I'll be damed if I'm going to get part three without a calculator I get : 36 + 3 + 68 + 47(10) + 36(8 ) = 107+470+288 = 867 for a starting set of numbers, so then: 867 + 100(3+7) + 867 + 100(3+7) + 867 + ... +100(4+7) +867 = 100(63+36) + 10(867) 9900+ 8670= 18570 for...
Fri Dec 22, 2006 9:42 am UTC
Forum: Logic Puzzles
Topic: The Narcoleptic Bookworm: Solution Thread
Replies: 14
Views: 5358
If my books are backwards, just switch the volume names. Same solution applies, he just ends up in 5 instead of 1. Emerald Hawk , I can't speak for pvtveite , but I ruled out 200 ppm BECAUSE it has no unique solution. Surely the intention was that he ends up in some specific volume, so a speed or po...
Tue Dec 19, 2006 2:02 pm UTC
Forum: Logic Puzzles
Topic: Missed the Train
Replies: 3
Views: 2694

### Missed the Train

Twice a day I sign on to the xkcd forum (at regular intervals) and stay until someone posts in either Logic Puzzles or Comic Threads (mine don't count!). An overwhelming majority of the time, 9/10 by my count, I end up leaving after a Comics post. Yet, at the end of the week, there are as many Logic...
Tue Dec 19, 2006 1:27 pm UTC
Forum: General
Replies: 1607
Views: 193434
I do not have toenails on my big toes. Many years ago, I had a bad habit of clipping my toenails way too short (part of some sort of 'peeling' complex I have). They became ingrown and were removed, with the root killed. Now, no more toenails. You ought to get in contact with Karl Pilkington, he'd l...
Tue Dec 19, 2006 11:03 am UTC
Forum: General
Topic: Songs that you get 'obsessed' with.
Replies: 156
Views: 33122
Well, a bit late, but hey, it got bumped, so: Country Roads, Take Me Home. Once I saw "Whisper of the Heart", I've listened to every version I have (John Denver, Me First and The Gimme Gimmes, a house/dance remix of John Denver's, and a local musician's version) and I've been looking for O...
Tue Dec 19, 2006 9:04 am UTC
Forum: Logic Puzzles
Topic: The Narcoleptic Bookworm: Solution Thread
Replies: 14
Views: 5358
I arrange the books on my shelf so that the first volume is the rightmost (ie 54321), so that when I turn my head to the right, I can read the title (CDs work the same way, mostly). If the problem is of that sort, then just reverse everything to the way you read it in your backwards country.
Tue Dec 19, 2006 8:43 am UTC
Forum: Logic Puzzles
Topic: Mathematical aliens again
Replies: 12
Views: 6295
Well, an unsolvable puzzle is not really a puzzle at all. I contend that my interpretation IS the actual puzzle, and that it's just been lost somewhere along the way. Otherwise, I challenge a solution of the puzzle as stated, and with that, I'd like to know where A, B, C or D fail, as those are the ...
Tue Dec 19, 2006 1:42 am UTC
Forum: Logic Puzzles
Topic: The Narcoleptic Bookworm: Solution Thread
Replies: 14
Views: 5358
I tried this out with some nice numbers for speed and volume size, but I bet a general solution would look the same. At a speed of 300 pages/minute, and if every volume has 500 pages, then V3 must be moved next to V1, so that he can travel through the back cover of V3 and get to page 200 of V1. Then...
Tue Dec 19, 2006 1:01 am UTC
Forum: Logic Puzzles
Topic: Mathematical aliens again
Replies: 12
Views: 6295
I'm not so sure about this one. Looking at the other question, I agree with V , this is a distinctly different puzzle, and it seems like it can be solved similarly, but when I get to the last step, it doesn't resolve. To start, Tom knows that Harry does not know the numbers, so the sum cannot be A) ...
Sat Dec 16, 2006 3:45 pm UTC
Forum: Logic Puzzles
Topic: The Man Who Shot Liberty Valance - [solutions]
Replies: 15
Views: 5962
Don't read this if you want to think about it more. Here's a hint: they're not dividing the water just to look at it. "Wayne cannot give either of his new cups to Marvin without breaking rule B". But if he could, it'd work out. This is by no means the most efficient solution. In fact, I th...
Sat Dec 16, 2006 1:32 pm UTC
Forum: Logic Puzzles
Topic: The Man Who Shot Liberty Valance - [solutions]
Replies: 15
Views: 5962
I agree, ABC is impossible. I don't see why either of
Dashiva wrote:the pouring 5/5 -> 0/3 (with 3/8 elsewhere) ... or ... the pouring 2/3 -> 0/5 (with 6/8 elsewhere)
has to happen.
Sat Dec 16, 2006 12:32 pm UTC
Forum: General
Topic: Moon Landing
Replies: 198
Views: 46655
I liked this part the best:
Twasbrillig wrote:Aldrin's response? He punched the man in the face.
I'd do it too if someone who didn't do his research questioned the greatest accomplishment of my life.
Sat Dec 16, 2006 12:26 pm UTC
Forum: Logic Puzzles
Topic: Choose a donut [solutions]
Replies: 4
Views: 3159
I was typing while you made this, so I put my solution in the other thread. Looking back at it, I find it's harder to follow the equations in white text, so here's it is again. The answer depends on how many people have no preference, like you, and how many try to get a donut. If you eat a glazed do...
Sat Dec 16, 2006 12:21 pm UTC
Forum: Logic Puzzles
Topic: Choose a donut
Replies: 2
Views: 3038
The answer depends on how many people have no preference, like you, and how many try to get a donut. If you eat a glazed donut, leaving one of each kind, then it takes any person, and a person without preference to eat both of them. Call this situation A. If you leave 2 of the same type, and assumi...
Sat Dec 16, 2006 8:39 am UTC
Forum: General
Topic: How do I....
Replies: 9
Views: 2792
Seems no one has ever had this problem before. So, everyone, what's your excuse? Greedy? Poor? Not convinced drawing stick figures is worth money? About time for a poll....
Sat Dec 16, 2006 8:24 am UTC
Forum: Logic Puzzles
Topic: The Man Who Shot Liberty Valance - [solutions]
Replies: 15
Views: 5962
The jar is not a standard shape. Every container has melted in the sun, and cannot be capped or otherwise covered by the other containers.