posted by Jim on .
what is the probability of rolling a matching pair of numbers when rolling a pair of dice?
I think it would be 1/12.
Each dice has 6 numbers, thus there is a 1/6 probability of rolling any number. When you roll the second dice you have the same probability of getting any number. Since you want the numbers to be the same you would multiple the probabilities of getting one number together. 1/6 x 1/6 = 1/12
First of all 1/6 * 1/6 = 1/36 ≠ 1/12
However, the matched pair can be 1s, 2s, 3s, 4s, 5s or 6s. The either-or probability is found by adding the individual probabilities.
1/36 + 1/36 + 1/36 + 1/36 + 1/36 + 1/36 = 6/36 = 1/6