Question

What is the probability that a sum of a pair of number cubes will be even and greater than 6 if the first cube lands on 4?

I guessed the answer to this question and got it right with 1/18 out of pure luck. I have no idea why it is 1/18! I'd love a quick explanation :D

Answer 1

Explanation:

If the first cube lands on a 4, then the second cube must land on 4 5 or 6.

It cannot land on 5 because that would make it the sum odd. (4 + 5 = 9)

So that leaves 4 and 6. You cannot use 2 because 4 + 2 = 6. The sum must be greater than 6.

So we are left with 2 results. The second cube should be 4 or 6

The results are 4 and 4

and 4 and 6

The results of throwing 2 dice are 36 ways in all. Only 2 combinations work.

2/36 = 1/18

I'm not sure that this is correct but it is the way done by the person writing the question.