You're quite right. When you use a single dice (twelve sided) the probability of getting any number (1 to 12 inclusive) is just 1/12. When you use two dices of 6 sides each the probability of each number is markedly different. 
Value      Probability      Combinations
   1            0
   2           1/36            1:1
   3           2/36            1:2, 2:1
   4           3/36            1:3, 2:2, 3,1    
   5           4/36            1:4, 2:3, 3:2, 4:1
   6           5/36            1:5, 2:4, 3:3, 4:2, 5:1
   7           6/36            1:6, 2:5, 3:4, 4:3, 5:2, 6:1
   8           5/36            2:6, 3:5, 4:4, 5:3, 6:2
   9           4/36            3:6, 4:5, 5:4, 6:3
  10           3/36            4:6, 5:5, 6:4
  11           2/36            5:6, 6:5
  12           1/36            6:6

[download]
Of course, if you're not using a truely random or very, very convincing pseudo-random generator you probably won't quite get these probabilities.

Considering that 7 is a bad number to get in Craps, it'd be nicer to use just a 12 sided dice, but then the Casinos would have to rig the game another way to get their money. ;)

It's good to know that for this kind of example rand() is as good as Math::Random.

jarich

In reply to Re: Re: Re: check my logic & a random number issue by jarich
in thread check my logic & a random number issue by rmckillen

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