Question

A pair of fair dice is rolled.

a. What is the probability of rolling a sum of 9?
b. What are the odds against rolling a sum of 9?

Answer 1

a) 4/36, or 1/9
b) 1-1/9=8/9

Answer 2

Sample space={6 x 6} = 36 possible outcomes:

Favorable outcome {(3+6),(4+5),(5+4),(6+3) = 4 favorable outcome:

P(getting a sum = 9) = 4/36 = 1/9 = 0.1111

the odds AGAINST = the number of failure/number of success

the odds AGAINST = 1/9