SOLUTION: Two dice are rolled. What is the probability of rolling the sum of 7? What about 7 OR 11?

Question 250304: Two dice are rolled. What is the probability of rolling the sum of 7? What about 7 OR 11?
Found 2 solutions by Greenfinch, drk:
Answer by Greenfinch(383) (Show Source): You can put this solution on YOUR website!
To do this use a Sample Space diagram. With it the problem is ridiculously simple, without it it is not at all easy. Number is the addition of the values
Value of first die across top, value of second die down the side
1 2 3 4 5 6
-----------------------
1 | 2 3 4 5 6 7
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
There are 6 x 6 or 36 options, all are equally likely, 7 occurs 6 times, so the chances are 6/36 or 1/6. 11 occurs 2 times so chances are 2/36 or 1/18. 7 or 11 are 8 of the 36 options so 8/36 or 2/9. You can even find out chance of a prime number. the 2,3,5,7,11 options add up to 15, so 15/36 or 5/12 is the chance of that.
Answer by drk(1908) (Show Source): You can put this solution on YOUR website!
There are 6 ways to get a 7 and a total of 36 ways for 2 dice, so
P(7) = 6/36 = 1/6
--
There are 2 ways to get a sum of 11. So,
P(7 OR 11) = 6/36 + 2/36 = 8/36 = 2/9.
--
OR means add (+)
AND means multiply (*)
RELATED QUESTIONS
If two standard dice are rolled, what is the probability of rolling doubles or a total... (answered by ikleyn)
Two fair six-sided dice are rolled. What is the probability that the sum of the... (answered by Boreal)
To the nearest hundredth, what is the probability of rolling a sum of 6 if two dice are... (answered by MathLover1,ewatrrr)
Two dice are rolled together. What is the probability of rolling a prime... (answered by nyc_function)
a pair of dice is rolled and the sum of the dice is found. what is the probability of... (answered by swincher4391)
two standard dice are rolled. what are the odds against rolling a sum of 4 or... (answered by josmiceli)
two dice are rolled. What is the probability that the sum is less than... (answered by solver91311)
a pair of dice is rolled. What are the odds against rolling the sum of... (answered by stanbon)
If two standard dice are rolled, what is the probability of rolling doubles or a total... (answered by ikleyn)