Toss 2 dice, and let the event be the sum of the values of the top faces. The possible outcomes are computed insde the following table at the intersection of the row of the "toss of 1st die" and the column of "toss of 2nd die":

toss of 2nd die

1 2 3 4 5 6

toss of 1 2 3 4 5 6 7

1st die 2 3 4 5 6 7 8

3 4 5 6 7 8 9

4 5 6 7 8 9 10

5 6 7 8 9 10 11

6 7 8 9 10 11 12

Because there are 36 outcomes, the probability of a sum= frequency of the sum /36.

so, the probability of the sum are:

sum probability:

2 1/36

3 2/36

4 3/36

5 4/36

6 5/36

7 6/36

8 5/36

9 4/36

10 3/36

11 2/36

12 1/36

only one of the sums 2 through 13 can occur in a single toss of the dice. These are mutually exclusive. The simple addition rule P(A or B) + P(B applies).

Match the items on the left to the items on the right (1 through 3):

0.000 1. P(X at least 7)

0.583 2. P(X is not 9)

0.889 3. P(X-1)