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Mutually exclusive events cannot happen at once, so their probabilities add: P(A or B) = P(A) + P(B), and an exhaustive set sums to 1. This topic identifies and calculates with them. It's examined right across GCSE and iGCSE Maths. Work through it free on eClassroom, with clear worked examples and instantly-marked questions that build your confidence for the exam.
How you do it
If two events cannot happen at the same time, add their probabilities. If they can, adding double counts the overlap. Check whether the events can occur together before you reach for the addition rule.
Before you start
Start once you are confident with basic probability. This is a Foundation and Higher tier topic. From here the path runs to the addition rule and Venn diagrams.
What you learn
Two events are mutually exclusive if they cannot happen at the same time. For these events you can simply add the probabilities. Two events are mutually exclusive if they cannot both happen at once — e.g. If mutually exclusive events cover every possibility (they are exhaustive), their probabilities add up to 1. P(milk or dark) = 0.5 + 0.3 = 0.8; P(not white) = 1 − 0.2 = 0.8. The course works through mutually exclusive events, exhaustive events sum to 1 and putting it together. Every section has instant-feedback practice questions matched to Edexcel iGCSE 4MA1 and the other major GCSE boards, and the course finishes with full exam-style questions you mark yourself.
Related Topics
Mutually Exclusive Events is a Probability topic in the GCSE syllabus, covered here at Foundation tier. There are 3 teaching sections and 2 fully worked examples, plus 3 sets of check questions. It sits alongside Relative Frequency, Sample Space Diagrams, Tree Diagrams, Two-Way Tables and Venn Diagrams in the same strand. Endless extra practice on this strand is available on the Probability revision engine, which generates a fresh question each time.
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