Two fair dice are rolled and the number of dots facing up is

Two fair dice are rolled and the number of dots facing up is added. Fill in the column for the probabilities.

X= sum of the dots facing up

P(X)

2

3

4

5

6

7

8

9

10

11

12

Solution

Note that there are 6*6 = 36 ways to roll 2 dice.

Thus, to get the probbaility of a sum, we count the number of ways it can be done, then divide it by 36.

For example, a sum of 3 can be done in only 2 ways, that is, (1,2) and (2,1). Hence, it has probability of 2/36.

Now, consider the table: