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## #1 2013-03-30 10:24:48

Al-Allo
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### help

hi

If I have the 1 circle, 3 triangles and two hexagons and they're in a bag and pick them two times with return what is the probability of getting exactly one hexagon ?

I get 3/9 but the answer is 4/9....

help pls thanks

## #2 2013-03-30 10:33:03

bobbym

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### Re: help

Hi;

4 / 9 is the correct answer.

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 2013-03-30 10:33:57

Al-Allo
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### Re: help

Could you explain me how you did it ? I get 12/36 and not 16/36....

## #4 2013-03-30 10:37:08

bobbym

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### Re: help

Hi;

For school problems you should be using the simplest ideas, especially when you are stuck. Did you draw a tree?

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.

## #5 2013-03-30 10:40:05

Al-Allo
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### Re: help

yes. and what do you mean by simplest ideas ?

## #6 2013-03-30 10:44:28

bobbym

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### Re: help

You always have to get an answer. One way, or the other.

Let me show you how to draw the tree without drawing it:

This is your set of possibilities,

now the triangles and the circle we are not interested in so we give them the generic label of "other." Your set becomes,

the tree looks like this,

oh
ho
oo
hh

do you follow?

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.

## #7 2013-03-30 10:47:55

Al-Allo
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### Re: help

ok...

explain this
oh
ho
oo
hh

Last edited by Al-Allo (2013-03-30 10:48:30)

## #8 2013-03-30 10:50:59

bobbym

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### Re: help

Hi;

oh = ( 4 / 6 ) ( 2 / 6 )
ho = ( 2 / 6 ) ( 4 / 6 )

oo = who cares
hh = who cares

Can you finish that?

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.

## #9 2013-03-30 10:54:49

Al-Allo
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### Re: help

it gives 16/36

but i still don't understand the logic behind it   how did you get those numbers ?ty

## #10 2013-03-30 10:59:58

bobbym

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### Re: help

ho means I drew a hexagon and then something else. The probability of drawing a h is 2 / 6 because there are 2 of them out of the total 6. Then I draw an o, the probability is ( 4 / 6 ) because there are 4 of them out of 6. Same logic for oh.

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.

## #11 2013-03-30 11:09:30

Al-Allo
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### Re: help

i think im gonna re read the problem... im not sure of even understanding what they want ..ty for your help

## #12 2013-03-30 11:13:09

bobbym

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### Re: help

If you are not sure of the problem then please just copy it over here.

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.

## #13 2013-03-30 11:22:11

Al-Allo
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### Re: help

Here :

An aleatory experience consists of turning an arrow on a roulette two times. (3 triangles, 1 circle, and two hexagon)

Question : What is the probability of obtaining exactly one haxagon.

## #14 2013-03-30 11:34:57

bobbym

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### Re: help

The question is the same as the one you posted in post #1. The answer and logic are the same, 4 / 9. I can draw a tree if it will help.

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.

Al-Allo
Full Member

Offline

## #16 2013-03-30 11:57:45

bobbym

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### Re: help

Here is the full tree do you know what to do from here? Pay no attention to the numbers after the words circle triangle or hexagon.

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.

## #17 2013-03-30 12:08:48

Al-Allo
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### Re: help

anyway, ill go through what you posted tomorrow, i dont have the energy tonight to think about it. thanks for your efforts to help.*curiously, when you get stuck on problems, how do you operate to solve them? any principles,etc. ?

## #18 2013-03-30 12:19:05

bobbym

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### Re: help

For probability and combinatorics when stuck I do it the hard way. No calculations, draw trees or count them all by hand.

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.