Mathematics for IGCSE & O level - Probability (Section 7 - No. 29)
What is the relationship between the probability of an event occurring and the probability of the event *not* occurring?
They are always equal.
They add up to 1.
They multiply to equal 1.
They are always opposite.
הֶסבֵּר
The probabilities of all possible outcomes for an event must sum to 1.