Probability sum

Question

If two fair dies or rolled find the probability that the sum of the dice is nine given that the sum is greater than three

Answer 1

There are 36 possible combinations. The only way to roll less than 3 is (1,1) (1,2) and 2,1) so there are 33 (36-3)ways to roll more than 3.

There are 4 ways to roll a 9 ( 3+6) (6+3) (5+4) and (4+5)

So given that you have rolled a number >3 the odds that it is a nine are 4/33