Probability Identities (Grade 10 NSC Matric Mathematics): Flashcards

Set of all possible outcomes in a probability experiment

$P(S) = 1$

$P(A \cup B) = P(A) + P(B) - P(A \cap B)$

Probability that either event A or B (or both) occurs

To avoid double-counting the overlap

Outcomes that belong to both events A and B

$P(E) = \frac{n(E)}{n(S)}$

Between 0 and 1

Add the parts, subtract the overlap

Help visualise why we subtract the intersection