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Originally Posted by fromia   Well I want to ask what is the difference between Multiplication and Addition rules and when to use them to find out the probabilities of events' occurence. For example: When you toss two coins what's the probability that they are heads up?
Thank you for helping me.  |
You use multiplication when the two events are independent of one another. In the case of flipping coins, the probability that a coin is heads-up is 1/2. So the probability of flipping two coins heads-up is (1/2)(1/2) = 1/4. You add distinct probabilities when you want to find the probability of an event that encompasses several probabilities, such as: What is the probability of drawing an 8 or a 9 from a standard deck of 52 cards? It is the same as the probability of drawing an 8 plus the probability of drawing a 9.