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#1 2010-09-14 05:10:29

samuel baffoe
Member
Registered: 2010-08-25
Posts: 5

probability

1) A man is given n keys, in random order of which only one will unlock his door. He tries them one by one (without replacement). find P(man succeeds on k*th trial)

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#2 2010-09-14 08:35:12

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 87,249

Re: probability

Hi Sam;

A question for you, you have posted several other questions.
I don't know whether or not you needed help or you were just posing a problem.
I answered them, can you check them and tell me what you think?


In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

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#3 2010-12-11 15:00:48

noemi1982
Member
Registered: 2010-12-11
Posts: 5

Re: probability

una clase consta de 14 hombres y de 30 mujeres de los cuales la mitad de los hombres y la mitad de las mujeres usan anteojos. Hallar la probabilidad de que una persona escogida al azar 1) sea hombre 2) use anteojos 3) sea hombre y use anteojos.
probabilidad por medio de Laplace

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#4 2010-12-11 15:03:31

noemi1982
Member
Registered: 2010-12-11
Posts: 5

Re: probability

en un experimento se tira 4 veces seguida una ficha de 2 caras, una roja y la otra blanca. calcular la probabilidad de:
1/ obtener exactamente una cara roja
2/ por lo menos una cara roja
3/ ninguna cara roja. hacer el conteo de los casos

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#5 2010-12-11 15:20:20

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 87,249

Re: probability

Hi noemi1982;

noemi1982 wrote:

una clase consta de 14 hombres y de 30 mujeres de los cuales la mitad de los hombres y la mitad de las mujeres usan anteojos. Hallar la probabilidad de que una persona escogida al azar 1) sea hombre 2) use anteojos 3) sea hombre y use anteojos.
probabilidad por medio de Laplace

Welcome to the forum! I do not understand what you mean by the method of Laplace.

Here are my answers:

1) P( is a man ) = 14 / 44

2) P(wears spectacles) = 1 / 2

3) P( is a man and uses spectacles ) = 7 / 44


In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

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#6 2010-12-11 15:43:53

noemi1982
Member
Registered: 2010-12-11
Posts: 5

Re: probability

regla de Laplace: se aplica cuando los "n" resultados son equiprobables.
P(A)= numero de caso favorable / numero de casos posibles

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#7 2010-12-11 15:49:53

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 87,249

Re: probability

Hi;

I understand. Then my answers in post 5 are correct, if I am translating correctly. I hope so.

I use P = successes / ( successes + failures ).


In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

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#8 2010-12-11 16:08:06

noemi1982
Member
Registered: 2010-12-11
Posts: 5

Re: probability

en un experimento se tira 4 veces seguida una ficha de 2 caras, una roja y la otra blanca. calcular la probabilidad de:
1/ obtener exactamente una cara roja
2/ por lo menos una cara roja
3/ ninguna cara roja. hacer el conteo de los casos
thank smile

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#9 2010-12-11 17:18:50

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 87,249

Re: probability

Hi;

I am sorry, I was able to understand your other posts because I had my brother to help translate. I do not understand spanish as well as he does. I think you are saying you flip a card 4 times and one side is red and the other side is white? Am I close?


In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

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#10 2010-12-12 03:10:48

noemi1982
Member
Registered: 2010-12-11
Posts: 5

Re: probability

In an experiment if you throw a double faced chip four times in a row with one face red and the other white.
Calculate the probability of:
1/exactly getting a red face
2/getting at least one red face
3/get no red faces
account the cases.
thanks

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#11 2010-12-12 05:29:51

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 87,249

Re: probability

Hi noemi1982;

Thanks for translating for me. I am learning a little spanish but I am a slow learner. I am going to assume that the probabilities of either face are equal.Okay we have a binomial experiment.

1) P(getting 1 red face) = 1 / 4

2) P(getting at least 1 red face) = 15 / 16

3) P(getting 0 red faces) = 1 / 16


In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

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