Multiplication rule for independent events
SAT glossary · Course Foundations
Definition
P(A and B) = P(A) × P(B), valid only when the events are independent — when one occurring does not change the other's probability. Applying it to dependent events is the trap.
Multiplication rule for independent events in plain English
The multiplication rule says that for two INDEPENDENT events (meaning one happening has zero effect on whether the other happens), the probability of both happening is just P(A)× P(B) — you literally multiply their individual chances together. The catch is that giant word 'independent': this formula only works when the two events truly don't affect each other at all. If the events ARE connected (dependent), multiplying their plain individual probabilities gives you a wrong answer, because one event happening actually changes the odds of the other — and using this shortcut anyway, when it doesn't apply, is exactly the trap these questions set.
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