Generally speaking, there are several ways to emphasize probability:
1: Direct demand for pure violence
The total number of possible situations in * * * is B, and the situation that meets the requirements of the topic in the above situation is A, so P = a/b means as many as taking C directly.
2. Need some skills to find a solution.
2. 1 addition principle: Available when two (n) events are independent of each other by adding probabilities. For example, the probability of eating an apple is 1/2, and the probability of eating a pear is 1/3, so the probability of eating is 1/3+ 1/2 = 5/6. It should be noted that the word "independent" means that I "eat apples" and "eat pears" are completely two things and cannot happen at the same time.
2.2 Multiplication principle: When two (n) events are interrelated, it is usually understood that there is a sequence, and the method is to multiply them. For example, the probability of eating an apple is 1/2, and the probability of eating a pear is 1/3, so the probability of eating an apple and a pear is 1/6. As you can see, I ate an apple first, so the probability value is 1/2, and then I ate pears on the basis of 1/2 (because I don't eat apples with a probability of 1/2), so the probability calculation method is1/2 *1.
Is that clear?