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Exercises 1-3 5
题目

There is one red, one yellow, one black ball each in the bag, and three draws are made with one replaced. Find the probability of the following events:

three times all the balls are red , 

three times no black balls are drawn ,

The colors are all different , 

The colors are not all the same .
解析

Solution: Base on the question, according to the multiplication principle, the total number of basic events is 

 

According to the classical concept and arrangement formula, there is 

,

,

,

Note that the colors are not all the same , then the colors are all the same , so, according to the property of probability 3, we have

.

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