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## #1 2017-03-11 15:00:30

hootyhoo
Member
Registered: 2017-03-11
Posts: 4

### Homework help? Deriving an expression for the probability...

Hi, all. I am not sure I put this put in the right category, but I'll ask anyways.

The problem I am stuck on tells me to consider a small machine with only two cups. And for that small machine I have to find out the probability of a ball landing in each cup. Then, I have to repeat this process for other machines with 3, 4, and 5 cups. From there I have to use any pattern I see and derive an expression for the probability of landing in the i^th cup from the left in a machine with n cups.

We also have to right the probabilities as fractions (not simplified) so we can find patterns.

Does anyone mind helping me with this?

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## #2 2017-03-11 16:31:06

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

### Re: Homework help? Deriving an expression for the probability...

Hi;

I would love to help but to help I need to see a bit of what you have already done and a bit of what you already know.

Some questions, how many balls are put into the cups? Are the cups equiprobable?

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 2017-03-11 17:17:31

hootyhoo
Member
Registered: 2017-03-11
Posts: 4

### Re: Homework help? Deriving an expression for the probability...

Oh yes, sorry for not including the number of balls. It's 40.

And this is what I have so far:

And for task one (the task before this one), I had to do an experiment using a pinball machine with 5 cups. (40 balls too):

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## #4 2017-03-11 17:46:55

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

### Re: Homework help? Deriving an expression for the probability...

Hi;

I have fixed your post to show the images. You do notice that this is close to a standard normal curve.

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 2017-03-11 18:30:30

hootyhoo
Member
Registered: 2017-03-11
Posts: 4

### Re: Homework help? Deriving an expression for the probability...

Now that you mention it, yes. And thank you for the fix.

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## #6 2017-03-11 18:46:01

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

### Re: Homework help? Deriving an expression for the probability...

I think you are attempting to build theoretically a quincunx.

http://www.mathsisfun.com/data/quincunx.html

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 2017-03-11 19:57:13

hootyhoo
Member
Registered: 2017-03-11
Posts: 4

### Re: Homework help? Deriving an expression for the probability...

Okay, I can see that now. I have neber heard of a quincunx so I looked more into it using this page: link removed by moderator

It says the forumla to solving the probability of a machine like this is binomial distribution. I will try making an expression witht aht and then I will let you know how it goes.

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## #8 2017-03-11 20:16:31

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

### Re: Homework help? Deriving an expression for the probability...

That page just leads me to a link with a bunch of gals in various stages of eating disorders...

Post when you are done and good luck.

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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