1. Pair of dice is rolled. What is the probability that the sum of the numbers rolled is either 7 or 11?
----------------
The possible sums are 2 to 12 inclusive ---> 11 possibilities.
Label the dice A and B:
For a sum of 7:
A B
1 6
2 5
3 4
4 3
5 2
6 1
6 of 11 ---> 6/11
For a sum of 11:
A B
5 6
6 5
2 possibilities ---> 2/11
7 or 11 ---> 8/11
====================================
2. A pair of dice is rolled. What is the probability that the sum of the numbers rolled is either an even number or a multiple of 3?
--------
Use the same method to find a sum of 2, 4, 6, 8, 10 or 12, or 3, 6, 9 or 12.
Note that 6 & 12 are even and a multiple of 3,
so the sums to find are 2, 3, 4, 6, 8, 9, 10 or 12.
=====================
Ikleyn didn't show where I am wrong.