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What is the formula of wide-angle set of mathematics in grade three?
"Unit" positioning, "Ten" positioning and exchange method in positioning methods. For example, 1, 2,3 form a two-digit number, and the ten digits and the single digits of each two-digit number cannot be the same.

The same class or the same thing or the same behavior, for example, the students in grade three are a collection, because the boys in grade three are also a collection, and a large collection can contain many small collections.

A representation of a set.

1. enumeration: the method of enumerating the elements of a collection one by one and enclosing them with braces "{}" is called enumeration.

2. Description method:

Definition: The method of representing a set with the * * * same characteristics of the elements contained in the set is called descriptive method.

Writing: Write the general symbols and the range of values (or changes) of the elements in this set with curly braces, then draw a vertical line, and write the * * * same characteristics of the elements in this set after the vertical line.

3. Graphical method, also called Venn diagram.

4. Interval representation: used to represent continuous number sets. A chapter on the three elements of function will appear in the textbook.