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#1 2015-05-10 04:36:23

Nemexia
Member
Registered: 2015-05-10
Posts: 13

probability

imagine we have 300 different balls possible, at least how many balls should we have so we be sure more than 50% that we have two balls with same color?
i guess the equation would be this (not sure):

300 * C(n,2) * (1/300)^2 * (299/300)^(n-2)   ≥  0.5

and i got answer 19


can anyone solve it?

Last edited by Nemexia (2015-05-10 04:38:20)

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#2 2015-05-10 07:34:32

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: probability

Hi;

Are there 300 different colors? How are the balls colored?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#3 2015-05-10 23:25:57

Nemexia
Member
Registered: 2015-05-10
Posts: 13

Re: probability

yes 300 different colors.
original question is:
there can be 300 types of neuron in a nerve, how many neuron should be in a nerve so we be sure more than 50% that we have two neuron with same type in that nerve?

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#4 2015-05-11 07:32:55

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: probability

Hi;

There are how many of each color?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#5 2015-05-11 23:00:29

Nemexia
Member
Registered: 2015-05-10
Posts: 13

Re: probability

well, just the type matters, i mean we have infinit amount for each color.

Last edited by Nemexia (2015-07-05 19:36:31)

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#6 2015-05-12 09:25:22

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: probability

Hi;

I am getting:

which yields an answer of n = 21


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#7 2015-07-05 19:28:03

Nemexia
Member
Registered: 2015-05-10
Posts: 13

Re: probability

Thanks, its correct. Can you please tell me how you found this? Please

Oh i got it thanks!

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#8 2015-07-06 10:17:36

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: probability

Hi;

Let me know if you need more...


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#9 2015-07-16 06:25:38

Nemexia
Member
Registered: 2015-05-10
Posts: 13

Re: probability

But i can't still solve for n
Any way to do it?

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#10 2015-07-16 10:40:25

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: probability

Can you do trial and error?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#11 2015-07-16 18:17:35

Nemexia
Member
Registered: 2015-05-10
Posts: 13

Re: probability

No,

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#12 2015-07-16 18:18:38

Nemexia
Member
Registered: 2015-05-10
Posts: 13

Re: probability

I mean I shouldn't do that in this problem

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#13 2015-07-16 18:41:30

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: probability

Do you know that not every equation can be solved by algebraic means? This is one of those.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#14 2015-07-18 07:19:12

Nemexia
Member
Registered: 2015-05-10
Posts: 13

Re: probability

Oh, OK thanks

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#15 2015-07-18 07:47:19

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: probability

You might possibly be able to get a decent approximation from an iteration. That would require a computer.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Offline

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