((1+2)/3)^4 * 5 +6 +7 -8 -9

Edited to add extra pair of brackets.

## Search found 2051 matches

- Thu Feb 18, 2016 8:18 pm UTC
- Forum: Logic Puzzles
- Topic: Simple maths problem?
- Replies:
**9** - Views:
**2548**

- Thu Feb 18, 2016 8:07 pm UTC
- Forum: Logic Puzzles
- Topic: Simple maths problem?
- Replies:
**9** - Views:
**2548**

### Re: Simple maths problem?

Isn't that rather easy?

1+2+3+4-5+6+7-8-9

1-2-3+4+5+6+7-8-9

1+2+3+4+5-6-7+8-9

1+2-3-4+5-6+7+8-9

1+2+3+4-5+6+7-8-9

1-2-3+4+5+6+7-8-9

1+2+3+4+5-6-7+8-9

1+2-3-4+5-6+7+8-9

- Mon Feb 15, 2016 5:39 pm UTC
- Forum: Mathematics
- Topic: Combinatorics : Castle, rooms and doors
- Replies:
**14** - Views:
**2647**

### Re: Combinatorics : Castle, rooms and doors

If we find a general formula for nxn with 0,1,2,3,4 doors then we wil obtain 2 doors by substraction. Subtraction from what? The number of nxn configurations where all the rooms have the same number of doors? How will that be calculated? Anyway, here are the results that I got by computer: x 1 2 3 ...

- Sun Feb 14, 2016 11:15 am UTC
- Forum: Mathematics
- Topic: Combinatorics : Castle, rooms and doors
- Replies:
**14** - Views:
**2647**

### Re: Combinatorics : Castle, rooms and doors

I get 86 for 2x2. Starting from 54 for the 3-room"L", 11 have two open doors towards the fourth room (->11 options), 11 have no open door (->11 options), and 32 have one open door (->2*32 options), for a total of 86 options. Finding that number of 11 was not trivial, so I don't see an eas...

- Fri Feb 12, 2016 4:05 pm UTC
- Forum: Mathematics
- Topic: Cardinality of subset of the powerset of naturals
- Replies:
**5** - Views:
**1468**

### Re: Cardinality of subset of the powerset of naturals

But for c = 0, isn't there still no natural number k which describes the size of infinite elements of S? Yet, since there is only one set in S of size |k| for each k in N (because k^c = 1), S is now countable. To restate what arbiteroftruth is getting at: Your statement "for all k in N, there ...

- Tue Feb 09, 2016 1:16 pm UTC
- Forum: Logic Puzzles
- Topic: A question about stacking spheres
- Replies:
**2** - Views:
**1933**

### Re: A question about stacking spheres

I assume you can't just remove spheres again? Yes, that is what I meant but didn't actually specify. Let's see the bottom layer can only have a even number sticking up, and the 3x3 layer only an uneven number and if an uneven number is alredy occupied on the 2x2 layer then everything is fine. B...

- Tue Feb 09, 2016 10:36 am UTC
- Forum: Logic Puzzles
- Topic: A question about stacking spheres
- Replies:
**2** - Views:
**1933**

### A question about stacking spheres

From the same person who asked me a question about stacking dominoes , here is a question about stacking spheres. Suppose you want to build a square pyramid made up of 30 spheres. So the bottom layer is a 4x4 arrangement of touching spheres, and it has 3x3, 2x2 and 1x1 layers on top. The building bl...

- Mon Feb 08, 2016 4:15 pm UTC
- Forum: Mathematics
- Topic: Coin flip problem
- Replies:
**6** - Views:
**1438**

### Re: Coin flip problem

With that you should be able to follow the rest of Cauchy's post that transforms that second term, the probability of a sequence that reaches m but ends below it, into the probability of a sequence that ends above m. I appreciate that you assumed I was the one explaining, but it just ain't so. Cred...

- Mon Feb 08, 2016 9:25 am UTC
- Forum: Mathematics
- Topic: Coin flip problem
- Replies:
**6** - Views:
**1438**

### Re: Coin flip problem

This is a trick I learned once for the "drunkard's walk" formulation. Let X k equal the number of heads minus the number of tails after k tosses. The probability that X k stays below m forever is equal to P(X n < m) - P(X n < m and X k = m for some k). For each sequence of flips in the la...

- Thu Feb 04, 2016 1:21 am UTC
- Forum: Movies and TV Shows
- Topic: Star Wars: Episode 7: Electric Boogaleven
- Replies:
**479** - Views:
**101336**

### Re: Star Wars: Episode 7: Electric Boogaleven

Well Cloverfield clearly hasn't vanished down the memory hole yet if you're mentioning it... People know it existed, sure. But nobody cares about it. Nobody thinks back and says "man, you know what was a good movie?" In twenty years, people won't even remember it was a thing unless they s...

- Fri Jan 15, 2016 5:48 pm UTC
- Forum: Logic Puzzles
- Topic: A question about stacking dominoes
- Replies:
**5** - Views:
**1902**

### Re: A question about stacking dominoes

So you need atleast 2x dominoes to support x dominoes. Anyway let's start building in the reverse direction, if you can add a valid layer below a layer you could have done it the other way around. I assume that adding dominoes to the layer below that don't support any stone does not improve...

- Fri Jan 15, 2016 5:35 pm UTC
- Forum: Logic Puzzles
- Topic: Unusual Cake Slicing
- Replies:
**84** - Views:
**17554**

### Re: Unusual Cake Slicing

Here is a dissection I found that I believe to be new, which is completely unrelated to any of the ones in this thread or in the paper.

Edit:

Colin Wright pointed out that this is an extreme case of the infinite family in the paper:

Edit:

Colin Wright pointed out that this is an extreme case of the infinite family in the paper:

- Fri Jan 15, 2016 3:49 pm UTC
- Forum: Logic Puzzles
- Topic: A question about stacking dominoes
- Replies:
**5** - Views:
**1902**

### A question about stacking dominoes

Here's a neat question someone asked me when he was developing a two-player game. Suppose you have a large number of identical 2x1 tiles, i.e. dominoes, and a large board with a square grid of the same size as the dominoes. You can place the dominoes on the board, but must follow these rules: ⋅...

- Thu Jan 14, 2016 7:06 am UTC
- Forum: Logic Puzzles
- Topic: Unusual Cake Slicing
- Replies:
**84** - Views:
**17554**

### Re: Unusual Cake Slicing

One year later, gizmodo catches up. http://gizmodo.com/mathematicians-have-found-crazy-new-ways-to-cut-pizza-i-1751776752 The paper was put on arxiv a month ago. It is doing the rounds now because New Scientist published an article about it last week. While the paper is from last year, I would not ...

- Wed Jan 13, 2016 6:40 pm UTC
- Forum: Logic Puzzles
- Topic: Unusual Cake Slicing
- Replies:
**84** - Views:
**17554**

### Re: Unusual Cake Slicing

There has been a new development: http://arxiv.org/pdf/1512.03794.pdf This paper shows some interesting new dissections of the circle into equal parts, not all on the boundary. It even references this thread. Still no solutions where the centre falls inside a piece, though. See also: http://www.ifls...

- Tue Jan 05, 2016 9:03 am UTC
- Forum: Movies and TV Shows
- Topic: Star Wars: Episode 7: Electric Boogaleven
- Replies:
**479** - Views:
**101336**

### Re: Star Wars: Episode 7: Electric Boogaleven

There's something in this movie's final fight that I'm sure I have seen before in some other film, but I can't think which one, namely the way Kylo Ren thumps his wounded side, as if to keep his body working Does anyone know where this was done before? Edit: I think it could be from a samurai movie,...

- Tue Jan 05, 2016 8:53 am UTC
- Forum: Logic Puzzles
- Topic: Blue Eyes with Superrationality
- Replies:
**48** - Views:
**9156**

### Re: Blue Eyes with Superrationality

Even though they all can agree that there is at least one blue-eyed person on the island, they don't mean the same thing when they say that. It really means, "amongst the N-1 people that are not me, there is at least one blue-eyed person". That statement is self-referential, and refers to ...

- Thu Dec 31, 2015 6:50 am UTC
- Forum: Logic Puzzles
- Topic: Probability of ending up in room N
- Replies:
**3** - Views:
**1935**

### Re: Probability of ending up in room N

Not really. You also have an infinite number of rounds to play, and each round has a non-zero chance of success. While it is theoretically possible to lose an infinite number of times, the probability of that happening is zero. You are almost surely going to win some round. What about this scenario...

- Wed Dec 30, 2015 10:27 am UTC
- Forum: Logic Puzzles
- Topic: Probability of ending up in room N
- Replies:
**3** - Views:
**1935**

### Re: Probability of ending up in room N

I've just "dreamt" this up, so if it's unsolvable (or even too easy) .... go easy on me please :) So you check into a plush hotel and pay your $40 for 1 night's stay. You are then told you've been allocated room 1 (which is a bit of a bummer. as the rooms get better as the room number inc...

- Tue Dec 29, 2015 12:14 am UTC
- Forum: Logic Puzzles
- Topic: Escape the bear in the circle?
- Replies:
**22** - Views:
**4857**

### Re: Escape the bear in the circle?

This is because your strategy would push the person closer and closer to the boundary. Even while moving in a circle, the bear can position itself to force the tangential direction of the prey's circular path to move towards the boundary. The tangential direction of the person's path, by definition...

- Sun Dec 27, 2015 9:02 am UTC
- Forum: Logic Puzzles
- Topic: Escape the bear in the circle?
- Replies:
**22** - Views:
**4857**

### Re: Escape the bear in the circle?

The explanations Notzeb linked to are suspiciously like the Zeno's paradox. At every step, the lion/bear gets closer to the person, yet it never fully overlap the person. Basically, the bear can get arbitrarily close, but never actually reach its prey. I agree that the proof in that paper there is ...

- Mon Nov 30, 2015 12:26 pm UTC
- Forum: Movies and TV Shows
- Topic: Doctor Whom
- Replies:
**4906** - Views:
**579176**

- Tue Nov 24, 2015 2:35 pm UTC
- Forum: Coding
- Topic: [Answered] Basic question about storing function results
- Replies:
**3** - Views:
**2878**

- Tue Nov 24, 2015 11:47 am UTC
- Forum: Mathematics
- Topic: Least numbers discarded when dealing cards
- Replies:
**30** - Views:
**5453**

### Re: Least numbers discarded when dealing cards

Do you understand what my method does? No, I have no idea what s % n function does. That is the 'mod' operator, and s%n means the remainder when dividing s by n. So 1000%52 = 12 because 1000=19*52+12. Perhaps if I add 52 to 52 until I find a number 100...00 it could be used in base 52. Though I'd s...

- Fri Nov 20, 2015 10:54 am UTC
- Forum: Mathematics
- Topic: Least numbers discarded when dealing cards
- Replies:
**30** - Views:
**5453**

### Re: Least numbers discarded when dealing cards

Am I missing something or are people way overthinking this? Just put the numbers 1 through 52 in an array and shuffle it. Dealing cards is as simple as pulling out elements starting from the first index and working your way down. The problem is that in step 2 of that shuffling algorithm you need to...

- Wed Nov 18, 2015 3:44 pm UTC
- Forum: Logic Puzzles
- Topic: Find the Mole
- Replies:
**5** - Views:
**2025**

### Re: Find the Mole

This is a repeat of:

viewtopic.php?f=3&t=62767

viewtopic.php?f=3&t=62767

- Mon Nov 16, 2015 9:33 pm UTC
- Forum: Coding
- Topic: Coding: Fleeting Thoughts
- Replies:
**9775** - Views:
**1602433**

### Re: Coding: Fleeting Thoughts

This discussion of for reminds me of this beautiful yet ghastly construct:

Code: Select all

`for(unsigned i = 10; i --> 0;)`

{

//stuff

}

- Thu Nov 12, 2015 9:31 am UTC
- Forum: Computer Science
- Topic: Reconstructing a tiling from "is-adjacent-to" data?
- Replies:
**10** - Views:
**6779**

### Re: Reconstructing a tiling from "is-adjacent-to" data?

By the way, the solution is usually not unique. For example, if you have 4 countries where each is adjacent to all three others, then you can draw a map in 8 distinct ways: You can choose any of the 4 countries to be in the middle, landlocked by the other three countries, and those other three can b...

- Wed Nov 11, 2015 11:16 am UTC
- Forum: Logic Puzzles
- Topic: Escape the Frictionless Circle
- Replies:
**156** - Views:
**36711**

### Re: Escape the Frictionless Circle

There is a loophole in the puzzle wording: A perfectly flat plane does not necessarily have to be perfectly level. If it's a sloping flat plane, you will automatically reach the outside of the circle. I also thought about what it means to have a perfectly flat surface on a round earth. Unfortuna...

- Tue Nov 10, 2015 6:23 pm UTC
- Forum: Computer Science
- Topic: Reconstructing a tiling from "is-adjacent-to" data?
- Replies:
**10** - Views:
**6779**

### Re: Reconstructing a tiling from "is-adjacent-to" data?

You can think of this data as a graph, where the countries are vertices and the 'is adjacent to' relation gives you the edges. Your question then boils down to this: Given a planar graph, draw it without any crossing edges. Or in more mathematical terms, find an embedding of a planar graph in the pl...

- Mon Nov 09, 2015 4:21 pm UTC
- Forum: Logic Puzzles
- Topic: Escape the Frictionless Circle
- Replies:
**156** - Views:
**36711**

### Re: Escape the Frictionless Circle

I wasn't clear there, I meant it wouldn't work for this puzzle's situation, not for a ball situation. If the floor can't distort here and the normal forces are all purely vertical, I don't see how the CoM of the system (gold block + person) can be shifted laterally. Sorry, for misunderstanding you....

- Mon Nov 09, 2015 3:08 pm UTC
- Forum: Logic Puzzles
- Topic: Escape the Frictionless Circle
- Replies:
**156** - Views:
**36711**

### Re: Escape the Frictionless Circle

The first thing that comes to mind is the answer to a problem that I read at some point: If a ball is rolling on an infinite, perfectly flat, surface, in a vacuum, will it ever stop? The answer was yes, because the ball exerts more force on the surface in the direction it is traveling in than the o...

- Fri Nov 06, 2015 5:28 pm UTC
- Forum: Logic Puzzles
- Topic: Timed Bridge Problem
- Replies:
**3** - Views:
**1789**

- Fri Nov 06, 2015 1:12 pm UTC
- Forum: Logic Puzzles
- Topic: Escape the Frictionless Circle
- Replies:
**156** - Views:
**36711**

### Re: Escape the Frictionless Circle

I thought for a moment that you could do this: Give the gold block some spin. Assuming you are a foot or two away from the gold block rather than directly on top of it, this will push you around the block in the opposite direction, so as soon as you let go of the block you will be moving away in a s...

- Wed Oct 28, 2015 6:01 pm UTC
- Forum: Mathematics
- Topic: Euler totient and powers of 2 minus 1
- Replies:
**10** - Views:
**1931**

### Re: Euler totient and powers of 2 minus 1

I was too slow, but here is my proof anyway: Start with Euler's Theorem , which says that a phi(m) = 1 mod m for any coprime integers a and m. For our purposes we choose a=2, and m=2 n -1, which are obviously coprime. So 2 phi(m) = 1 mod 2 n -1. The multiplicative order of 2 in the g...

- Mon Oct 26, 2015 1:39 pm UTC
- Forum: Mathematics
- Topic: Combinatorics : counting problem
- Replies:
**7** - Views:
**1722**

### Re: Combinatorics : counting problem

If I did not make a mistake I have found only 4 permutations repeating themselves : 2,3,4,5,6 6,5,2,3,4 4,3,2,5,6 6,5,4,3,2 The starting numbers are : 2,24,32,54,62,84,92,..... 2+22=24 24+8=32 32+22=54 54+8=62 62+22=84 84+8=92 Alternatively we add 22 and after 22 we add 8 and so on I do not know if...

- Thu Oct 15, 2015 12:50 pm UTC
- Forum: Movies and TV Shows
- Topic: Do you enjoy car chase scenes in movies?
- Replies:
**19** - Views:
**4931**

### Re: Do you enjoy car chase scenes in movies?

The classic Bullitt car chase scene has become a bit cheesy for me when it was pointed out that

I can't help but notice that now and, while still fun, that makes it cheesy fun instead of exciting fun.

**Spoiler:**

- Wed Oct 14, 2015 2:29 pm UTC
- Forum: Movies and TV Shows
- Topic: Do you enjoy car chase scenes in movies?
- Replies:
**19** - Views:
**4931**

### Re: Do you enjoy car chase scenes in movies?

One of the cool things about Fury Road was just that it was all real, actual stunts (even if the action happened to be sped up at some point in production). They thought they might have to use CGI for safety reasons, but I think pretty much everything (aside from the speed) was actually done -- the...

- Tue Oct 13, 2015 5:25 pm UTC
- Forum: Mathematics
- Topic: Congruences
- Replies:
**1** - Views:
**1202**

### Re: Congruences

Hi, While trying to solve a problem linked to a primality test I encountered another one. Here is my problem. I did some tests it works. n=2k+1 k>0 a=(2^(2k+1))-1 b=(2^(10k+5)-1) c=(2^(10k+5)+1) Show that either b = 0 mod a either c= 0 mod a Thank you for any clue. x 5 -1 = (x-1)(x 4 +x 3 +x 2 +x+1...

- Fri Oct 09, 2015 12:13 pm UTC
- Forum: Logic Puzzles
- Topic: Kirkman's Schoolgirls
- Replies:
**12** - Views:
**3174**

### Re: Kirkman's Schoolgirls

I think I have a solution. 05A 06C 07E 0B7 0C9 D08 E09 16B 17D 18A 1C8 1D5 E19 A15 27C 28E 29B 2D9 2E6 A25 B26 38D 39A 35C 3E5 3A7 B36 C37 49E 45B 46D 4A6 4B8 C47 D48 Note that 'abreast' in the original problem does not necessarily mean adjacent in a triplet. What is meant is that no pair of school...