The probability of an event that is certain to occur is 1.
This means that if you know an event will happen without any doubt, its probability can be expressed as the ratio of favorable outcomes to the total outcomes. In this case, since there are no unfavorable outcomes (the event will definitely happen), the formula simplifies to:
Probability (A) = Number of favorable outcomes / Total number of outcomes
For an event that is guaranteed to happen, the calculation would look like:
Probability (A) = 1 / 1 = 1
Thus, when an event is certain, it is assigned a probability of 1, indicating absolute certainty.