# Thread: Dice probability problem

1. ## Dice probability problem

Hi everyone,

I have a simple dice problem but am having trouble with it because it's hard to google something like this. Here it is...

I have 2 dice that I get to roll 1 time. What are the chances that I roll either of two specified numbers?

For example, with 2 dice and a single roll, what are the chances that I roll either a 1 or 2 with either of the two dice?

With 3 dice and 1 roll, what are the chances I get either a 1 or a 2? With 4 dice and 1 roll, what are the chances I get either a 1 or a 2?

I wish to compare that to this .... with 2 dice and 2 rolls, what are the chances I roll either of two specificed numbers? (with 3 dice and 2 rolls, etc)

Thank you for your help.

2. ## Re: Dice probability problem

The probability that you get either a "1" or a "2" with one die is 2/6
Letīs call this a sucess, or s
The probability that you get neither a "1" or a "2" with one die is 4/6
Letīs call this a failure, or f

We can now use the formula
and replace n with the number of rolls with the die

The probability that you get a sucess with 2 rolls is 55,5%
------------------------------------------------3 rolls is 70,3 %
------------------------------------------------4 rolls is 80,2 %
------------------------------------------------5 rolls is 86,8 %

3. ## The Following User Says Thank You to Becky1 For This Useful Post:

benali (12-16-2014)

4. ## Re: Dice probability problem

Becky, thank you so much. With the formula you've provided it's much more clear to me now.

I think I understand now that rolling 2 dice 2 times gives the same odds of rolling a specific number as does rolling 1 die 4 times --- since you're getting the equivalent of 4 total rolls of one die in both cases. In other words, each die roll is an independent event. So your formula describes either case.

Thank you again.

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