If you roll two standard number cubes what is the probability that the sum is odd, given that one of the number cubes shows a 4?

If one cube shows a 4, we know that the other cube must show an odd number in order for their sum to be odd.

On a standard die, there are 3 odd numbers and 3 even numbers.

Therefore, there's a 50% chance that the sum of the two cubes will be odd if one of the cubes shows a 4.