The Addition Rule
Learn to calculate the probability of one event OR another occurring. Apply the General Addition Rule, P(A or B) = P(A) + P(B) - P(A and B), paying special attention to mutually exclusive events.
About This Topic
Learn to calculate the probability of one event OR another occurring. Apply the General Addition Rule, P(A or B) = P(A) + P(B) - P(A and B), paying special attention to mutually exclusive events.
Key Questions
- Explain why we must subtract the probability of the intersection when using the Addition Rule for non-mutually exclusive events.
- Compare the Addition Rule for mutually exclusive events to the general rule.
- Analyze a problem to identify whether to use the Addition Rule or the Multiplication Rule.
Active Learning Ideas
See all activities→Activities & Teaching Strategies
See all activities
Planning templates for Mathematics
5E Model
The 5E Model structures lessons through five phases (Engage, Explore, Explain, Elaborate, and Evaluate), guiding students from curiosity to deep understanding through inquiry-based learning.
Unit PlannerMath Unit
Plan a multi-week math unit with conceptual coherence: from building number sense and procedural fluency to applying skills in context and developing mathematical reasoning across a connected sequence of lessons.
RubricMath Rubric
Build a math rubric that assesses problem-solving, mathematical reasoning, and communication alongside procedural accuracy, giving students feedback on how they think, not just whether they got the right answer.
More in Statistics and Probability
Understanding Independence and Conditional Probability
Explore the difference between independent and dependent events. Learn how the occurrence of one event can affect the probability of another, a concept known as conditional probability.
8 methodologies
Using Two-Way Tables
Organize data from a sample space into a two-way frequency table. Use the table to calculate joint, marginal, and conditional probabilities.
8 methodologies
Conditional Probability and Independence
Use the formal definition of conditional probability to calculate probabilities. Apply the test for independence, P(A and B) = P(A) * P(B), to determine if two events are truly independent.
8 methodologies
The Multiplication Rule
Find the probability of two or more events occurring in sequence. Apply the General Multiplication Rule, P(A and B) = P(A) * P(B|A), and its simpler version for independent events.
8 methodologies
Permutations and Combinations
Learn counting principles to determine the number of possible outcomes. Use permutations when order matters and combinations when it does not to solve complex probability problems.
8 methodologies