Tree diagram and list method like this are used to analyze probability and ratio. For example, there are five white, red and blue balls. Find the probability of touching three balls and two white balls at a time. So you need to make a list or draw a tree diagram to analyze the problem. You should know how to draw a tree diagram. Drawing a tree diagram is the best solution, and this kind of senior high school entrance examination is often taken. But it is also the type I have compared.

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