Edexcel A-level Maths Independent outcomes
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If the probability of a 1st event happening has no impact on the probability of a 2nd event happening then the two events are independent.
When finding the probabilities for independent outcomes, we can use the and rule. If event 1 happens AND event 2 also happens, we multiply the probabilities.
We can use the OR rule when calculating the probability of either of 2 different events occurring. If asked to find the probability of event A or event B happening, we must add the probabilities.
Charlie, Toby and Jamie attend a local drama session. The probabilities of them arriving late are, independently, 0.6, 0.3 and 0.1 respectively. Calculate the probability that only Toby arrives late.
There are 120 students on a university course. If a student fails either their exam or coursework they must resit the course exam. 94 students pass both the coursework and the exam. 16 students fail the exam and 14 students fail the coursework. Calculate the probability that a student chosen at random is resiting the exam.
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