WEBVTT

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Here is the problem: Independent events have P(A) equals 0.4 and P(B) equals 0.25. Find P(A and B) and P(A or B).

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Two independent events A and B.

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Both: multiply, because the events are independent.

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At least one: add and subtract the overlap.

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Exactly one of them.

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Neither.

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So the answer is P(A and B) equals 1 over 10 approximately 0.1; P(A or B) equals 11 over 20 approximately 0.55; P(neither) equals 9 over 20 approximately 0.45.

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For independent events the probability that both happen is the product of the individual probabilities.

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P(A or B) plus P(neither) equals 1 equals 1.