Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

## #1 2010-09-15 03:10:29

samuel baffoe
Novice

Offline

### 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)

## #2 2010-09-15 06:35:12

bobbym

Offline

### 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.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #3 2010-12-12 14:00:48

noemi1982
Novice

Offline

### 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.

## #4 2010-12-12 14:03:31

noemi1982
Novice

Offline

### 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

## #5 2010-12-12 14:20:20

bobbym

Offline

### 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.

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

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.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #6 2010-12-12 14:43:53

noemi1982
Novice

Offline

### Re: probability

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

## #7 2010-12-12 14:49:53

bobbym

Offline

### 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.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #8 2010-12-12 15:08:06

noemi1982
Novice

Offline

### 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

## #9 2010-12-12 16:18:50

bobbym

Offline

### 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.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #10 2010-12-13 02:10:48

noemi1982
Novice

Offline

### 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

## #11 2010-12-13 04:29:51

bobbym

Offline

### 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.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.