Math question: probability

[Mantus]

I need a little help here, my head isnt working today.

A chance of rolling any number on a die is 1/6.

Lets say I want to roll a “2”.

If I roll once there is a 1/6 chance of rolling a “2”.

How do I calculate the odds of rolling a “2” if I roll the dice ten times?

[Cowman]

rolling a two consecutively 10 times would be

1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1
---------------------------------
6 x 6 x 6 x 6 x 6 x 6 x 6 x 6 x 6 x 6 = 1/a really big number

however, I don't know about just rolling ot once

[CSflim]

Mantus: Do you mean what are the chances of rolling at least one 2 or rolling exactly one 2? I presume the former.

The easist way to do this is to think "what are the chances of me rolling NO 2s?"

On a single roll, the probability of not rolling a 2 is 5/6.
Hence the probability of not rolling a 2 ten times in a row is (5/6)¹⁰.

So the probability of NOT not rolling a 2 is one minus this:
1 - (5/6)¹⁰

[phukraut]

Because rolling the die is independent between trials, Cowman's got it right:

P(getting "2" on each roll after n rolls) = 1/6^n.

However, it's been a long time since I've done this stuff!

[CSflim]

Originally Posted by phukraut

Because rolling the die is independent between trials, Cowman's got it right:

P(getting "2" after n rolls) = 1/6^n.

However, it's been a long time since I've done this stuff!

That is the probability for rolling all 2s on ten rolls. I don't think that is what Mantus is looking for.

[skills1]

i THINK cowman's right. not sure, im not too hot in math.

[fckm]

see CSFilm's post. He's got it right. (Depending on what you mean by rolling a two)

[Shpoop]

yea the prize goes to csfilm

[itch vaccine]

--edit--

misread posts :P

[Mantus]

Sorry guys, that was proorly phrased.

I am looking the posibility of rolling at least one "2" out of 10 rolls.

[Strangehate]

For every 10 rolls you should roll 2, 1.67 times... if you are asking what the probability of rolling at least one 2 when you roll 10 times, it is basically 100% if not more than 100%...

[Pragma]

It's impossible to have more than 100% probability.

If you're asking what is the probability of rolling at least one 2 in 10 rolls, one of the above posters had it right:

Take the total probability (1) and subtract the probability of rolling NO 2s. The math works out to be about an 83.8% probability of rolling at least one two, not quit as high as you had anticipated.

[telekinetic]

Originally Posted by CSflim

Mantus: Do you mean what are the chances of rolling at least one 2 or rolling exactly one 2? I presume the former.

The easist way to do this is to think "what are the chances of me rolling NO 2s?"

On a single roll, the probability of not rolling a 2 is 5/6.
Hence the probability of not rolling a 2 ten times in a row is (5/6)¹⁰.

So the probability of NOT not rolling a 2 is one minus this:
1 - (5/6)¹⁰

I am just quoting this because it is correct, and if you work it out you get 83% just like the last poster mentioned

[Mantus]

Ah it just clicked in...I am very rusty with math. Perhaps it's time for me to take a class to refresh my memory, thanks guys