Two normal dice, one blue and one red rolled. the two results added together. What is the probability of getting a sum of 6, given that the blue die is even.

Question

kropot72 · Answer

The sample space has 36 possible combinations of numbers. These can be set out in column form as follows:
6,6  5,6  4,6  3,6  2,6  1,6
6,5  5,5  4,5  3,5  2,5  1,5
6,4  5,4  4,4  3,4  2,4  1,4
6,3  5,3  4,3  3,3  2,3  1,3
6,2  5,2  4,2  3,2  2,2  1,2
6,1  5,1  4,1  3,1  2,1  1,1

anonymous · Answer

Yes because you have two selections, its 6C1 x 6C1 so you have 36 total combinations.

kropot72 · Answer

However since we are given that the blue die is even, and taking the first of the pairs as the blue die result, there are 3 columns that apply. The sample space is just 18 possible combinations. How many of these sum to 6?

anonymous · Answer

I just solved it then, P(blue and even) = 36/2 = 18 possible combinations

anonymous · Answer

then p(sum of 6) = 5/36
however of those 5, two are even and blue.
therefore = 2/18

kropot72 · Answer

Of the possible 18 outcomes 2,4 and 4,2 add to 6. The probability is therefore 2/18 = 1/9

anonymous · Answer

Ok yes that is the right answer. How about P(Total of 5|at least one is even)

anonymous · Answer

I'm good with algebra, calculus etc is fairly easy for me, but i suck at probability.

kropot72 · Answer

Look at the each of the 36 possible combinations and write down those that total 5 with one either 2 or 4.