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Thread: Dice probability problem

  1. #1
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    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. #2
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    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 Name:  CodeCogsEqn.gif
Views: 58
Size:  280 Bytes
    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 %
    Last edited by Becky1; 12-16-2014 at 03:42 AM.

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

    benali (12-16-2014)

  4. #3
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    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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