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## #1 2014-04-24 09:34:49

evinda
Member
Registered: 2013-04-13
Posts: 105

### married couples-how many ways

Hello!!!:)
Could you help me at the following exercise?
With how many ways can we choose a man and a woman that are not married to each other from n married couples?

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## #2 2014-04-24 14:41:13

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 104,288

### Re: married couples-how many ways

Hi;

Empirically it looks like n^2-n.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
A number by itself is useful, but it is far more useful to know how accurate or certain that number is.

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## #3 2014-04-24 18:13:12

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

it is not empirical.

Consider n couples. Now, we have n men and n women.

Now, for every men there is one wife, which means that there are n-1 women not married to him.

For n men, there are a total of n*(n-1) choices.

bobbym,

What is your experimental method?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #4 2014-04-24 19:31:23

bob bundy
Moderator
Registered: 2010-06-20
Posts: 7,577

### Re: married couples-how many ways

What is your experimental method?

Maybe he assembled n married couples and asked them to pair up in new ways and recorded the results.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #5 2014-04-24 19:37:10

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

He could have done that. Here is his post on experimental teaching: http://www.mathisfunforum.com/viewtopic.php?id=20563

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #6 2014-04-24 19:41:52

bob bundy
Moderator
Registered: 2010-06-20
Posts: 7,577

### Re: married couples-how many ways

You think that post was about experimental teaching?  Surely it was just bad teaching.  Unless you think the teacher was choosing random explanations, comparing results and then selecting the most effective.  In that case, we are clearly witnessing the experiment at a very early stage.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #7 2014-04-24 19:58:12

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

Yes, very bad teaching indeed.

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #8 2014-04-24 21:55:06

ElainaVW
Member
Registered: 2013-04-29
Posts: 510

### Re: married couples-how many ways

Hello:

While bobbym cooks a late night snack for himself, he said I could answer this as long as I showed the proper respect.

Agnishom wrote:

it is not empirical.

He got the result by examining some actual experiments. That is what he meant by empirical. As you can see it was correct. Do you think he wasn't capable of the n(n-1) analysis? We are talking about the best combinatoricist here in Vegas. Why does he prefer empiricism and an Ansatz? The reason is simple because it will make short work on the tougher problems, the ones where reasoning will fail. Just take a look on how he answers the gAr problems and mine in the other threads.

Maybe he assembled n married couples and asked them to pair up in new ways and recorded the results.

That is exactly what he did but in virtual reality.

bob bundy wrote:

You think that post was about experimental teaching?

The post isn't about teaching but rather about Brad's ability or inability to solve a problem. His ability or inability to come up with an Ansatz. That is why it's all about experimental math. You are graded on how you answer the question.

Yes, very bad teaching indeed.

I took the quiz here where that was one of the type questions I actually failed to answer. What answers did you guys give?

Last edited by ElainaVW (2014-04-24 22:01:35)

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## #9 2014-04-24 22:02:58

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

Ansatz

What does that mean?

Do you think he was not capable of the n(n-1) analysis? We are talking about the best combinatoricist here in Vegas

ElainaVW, I did not criticise bobbym or his methods in the previous posts.

Let us talk about the late night snack, for a change.

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Online

## #10 2014-04-24 22:12:49

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

@EVW,
wait a moment...

Are you not going to Florida or Disneyland?

bobbym will become the best combinatoricist of Florida soon.

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Online

## #11 2014-04-24 22:21:10

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 104,288

### Re: married couples-how many ways

An ansatz is an educated guess that is verified later by its results.

We are talking about the best combinatoricist here in Vegas

Hmmm, such a compliment, something is up?! The Colonel is and was the best combinatoricist in Vegas. EVW and jimmyR are very good also. gAr is excellent. I am okay only because I am a bumpkin.

The snack she mentions was for me and only for me. She criticized my cooking therefore she got none.

Why was that post brought up? If I remember it did not engender much interest here. She is correct in that she gave the wrong answer.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
A number by itself is useful, but it is far more useful to know how accurate or certain that number is.

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## #12 2014-04-24 22:25:51

bob bundy
Moderator
Registered: 2010-06-20
Posts: 7,577

### Re: married couples-how many ways

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #13 2014-04-24 22:27:37

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

What quiz is she talking about? Who is the colonel?

bobbym wrote:

Hmmm, such a compliment, something is up?!

The snack she mentions was for me and only for me. She criticized my cooking therefore she gott none.

are you saying that I will get some if I tell that you are the best cook in Vegas?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Online

## #14 2014-04-24 22:30:15

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 104,288

### Re: married couples-how many ways

Someone we both know and I find unpleasant to talk about.

It is not uncommon when seeking a job or admission into a group that you are given a quiz to test your processing power.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
A number by itself is useful, but it is far more useful to know how accurate or certain that number is.

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## #15 2014-04-24 22:38:22

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

Why would it be unpleasant to talk about the second best combinatorist of Vegas?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Online

## #16 2014-04-24 22:48:16

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 104,288

### Re: married couples-how many ways

There is no link that I am aware of.

Math is not like say snooker. I was watching "The Rocket" yesterday and admiring his style. Although we do not play the exact same game his basic style is much better than mine. In math we do not have ratings thank the Lord.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
A number by itself is useful, but it is far more useful to know how accurate or certain that number is.

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## #17 2014-04-24 23:49:22

ElainaVW
Member
Registered: 2013-04-29
Posts: 510

### Re: married couples-how many ways

bobbym will become the best combinatoricist of Florida soon.

Vegas has about a million people, Florida has about twenty million and I am there too so that is very unlikely.

Bobby's methods are fine. He is a good programmer and knows more math than he admits but lets face cold facts. Everybody knows EM as he calls it is a young persons game. The feminine mind is more intuitive and more capable at those ansatze he loves so much.

Last edited by ElainaVW (2014-04-24 23:54:50)

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## #18 2014-04-24 23:54:53

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

That is like down rating bobbym

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Online

## #19 2014-04-24 23:57:20

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

You have a feminine mind, Elaina?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Online

## #20 2014-04-24 23:57:45

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 104,288

### Re: married couples-how many ways

Bobby's methods are fine. He is a good programmer and knows more math than he admits but lets face cold facts. Everybody knows EM as he calls it is a young persons game. The feminine mind is more intuitive and more capable at those ansatze he loves so much.

We shall see!

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
A number by itself is useful, but it is far more useful to know how accurate or certain that number is.

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## #21 2014-04-24 23:59:42

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

I thought bobbym uses the immobile computer more than the feminine mind?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Online

## #22 2014-04-25 00:03:56

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 104,288

### Re: married couples-how many ways

Where did you get a thought like that from? That is Doronian but it is not me.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
A number by itself is useful, but it is far more useful to know how accurate or certain that number is.

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## #23 2014-04-25 00:41:56

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

Which thought?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Online

## #24 2014-04-25 00:42:36

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 104,288

### Re: married couples-how many ways

That I would ever use an immobile computer...

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
A number by itself is useful, but it is far more useful to know how accurate or certain that number is.

Offline

## #25 2014-04-25 00:46:47

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 23,790
Website

### Re: married couples-how many ways

You do not? What do you do all the time then?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Online