Suppose a regular die is rolled. What is the probability of getting a 3 or a 6?
The probability of getting one or the other of those numbers is 1 in 3. The probability of getting 3 is 1 in 6. So is the probability of getting a 6.
If the die has 6 sides, then there is a 1 in 6 chance of getting any particular number. That is why there is a 1 in 6 chance (16.67%) of getting a 3 and the same chance of getting a 6.
But if you are asking what the chances of getting 3 or 6 (rather than 1, 2, 4 or 5), then you double the chances. That is because you have a 1 in 6 chance for both. That makes a 2 in 6 chance (you can also say this as 1 in 3 or 33.33%) for getting one or the other of the numbers you mention.
The outcomes for the regular die is (1,2,3,4,5,6)
The outcomes for getting 3 or 6 is (3,6)
Then the probability = 2/6= 1/3
When a dice is thrown there are 6 exclusive possiblities: Showing up of 1 or 2 which is favouring the event, or 3 or 4 or 5 or 6 which are not favouring or against the event . That is 6 possibilities of either favouring or not favouring the event.
Possibilities of favouring the event is showing up of 3 or 6, whhich is in 2 ways.
Therefore the required probability = possibilities favouring/ Possibolities favouring and not favouring = 2/6 =1/3.