Question

Two fair 6-sided dice are rolled. What is the probability the sum rolled is 9?

Answer 1

Each dice has six combinations which are independent. Therefore the number of possible outcomes will be 6*6 = 36. The probability of rolling a pair of dice whose numbers add to 5 is 4/36 = 1/9.

Answer 2

The probability is

(number of ways to roll a 9) / (total possible different rolls) .

Each cube can land in 6 different ways, so the total possible rolls = 36 .

How many different rolls can be a sum of 9 ?
I don't know. Let's countum:

Cube-A Cube-B
3 6
4 5
5 4
6 3

Did I miss any ? I don't think so. There are four (4) ways to roll a 9.

So the probability is 4 / 36 = 1/9 = 11.1%